Rainbow Cake and Unicorns

Update June 2012: detailed photos on how to make a Rainbow Cake are here.

Update April 2010: the activities and games I planned for M’s party are described in a separate post here.

At the end of her birthday party last year, M announced that she would be having a unicorn party for her next birthday. I didn’t realise that she was absolutely serious about this. I thought, “It’s a whole year away – she’s bound to change her mind.” But no, for a whole year M has stuck to her original intention and has been counting down the days until her unicorn party. 

You could argue that I’ve had a whole year to prepare, so why the sudden rush to get everything ready last week? Well, M may have had a solidly clear idea of the grand theme for her party, but she left the finer details entirely up to me. Not wanting to disappoint, I threw myself into turning our house into an enchanted forest in the hope that any passing unicorns might be tempted to pop in on the big day. We made glittery trees and rainbow streamers while M’s big sister created a welcoming poster for the front door.

Last year, M set her heart on a cake she saw in a book by Debbie Brown (here’s a warning to parents – only ever let your children see pictures of cakes that you’re happy to make yourself). Four being so much more grownupperer than three, M has now thankfully entered the chocolate frosting and smarties stage. I’m not so very far removed from the icing sugar cloud of despair that I miss those fondant modelling sessions yet … I’m quite happy to be doing chocolate and smarties.

I couldn’t resist giving the birthday girl a little surprise, though. From the outside, M’s cake looked perfectly normal (in a homemade sort of way) – a magical plastic unicorn standing amid swirls of white chocolate buttercream and scattered smarties. M’s seven little party guests looked on dutifully as M blew out her candles and I took a knife to cut into the cake.

unicorn cake

Hesitating before plunging in to make the first slice, I asked them all, “Do you know what happens when a unicorn stands on top of a birthday cake?”

“No,” they whispered with wide eyes.

“He makes a rainbow,” I told them, cutting into the cake.

rainbow cake cut


The next day, M sidled up to me and asked, “Mummy, how did the unicorn do that to my cake?”

Well, if there’s by any chance anyone left in the blogosphere who hasn’t come across a rainbow cake before now, I’ll explain my own take on the concept … just in case a unicorn happens to pass by and stand on another little girl’s birthday cake 😉 .

I’m not sure who had the original idea – there’s a box-mix version doing the rounds that appears to have started with this thread in the dubiously-named ‘Something Awful’ forums. Rejecting the layered box-mix and diet soda variety however, I based my own rainbow cake recipe on Farida’s beautiful Zebra Cake (stay tuned for more from Farida in an upcoming post).

I followed Farida’s instructions to make a yellow cake batter (whichever basic cake recipe you choose, it’s important that it’s one in which the batter doesn’t mix about too much during baking or you’ll end up with a muddy brown cake instead of a rainbow). Then, instead of dividing it into two parts and colouring one part with cocoa as Farida did, I divided the mixture between seven bowls (roughly 4 tablespoons of batter in each) and used my fondant paste dyes to colour each portion a different colour of the rainbow.

coloured batter

I then poured each rainbow batter in turn (starting with red) into the centre of my prepared cake pan. As Farida says, don’t wait for each colour to spread out before starting with the next – just pour the batter into the centre of the pan, then pour the next colour right on top and then the colour after that without waiting for each to spread fully. The weight of each batter pushes the previous colour out further and, as long as you keep a steady hand with the pouring, they all sort themselves out.

batter in pan

And it’s as simple as that.

I found out in the school playground this morning that one of the guests has kept her special piece of rainbow cake carefully wrapped up since the party so that she can show it to everyone who visits.

rainbow cake crumbs
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  1. Love it!
    What a fun surprise for the kids. I’ve actually not seen a rainbow cake before, thanks!

  2. Thanks, Aimee – I was so sure I’d be the last to find out about these cakes (I usually am!!) and that they’d be old news by now … I’m fully expecting to be shot down in flames by the god of all-things-natural, but it was fun to see the children’s faces when they saw the bright rainbow colours inside the cake!

  3. i can’t imagine a more delightful birthday cake for a little girl. even a big girl like myself finds it exquisitely dreamy/beautiful! bravo kate!

  4. Julie

     /  June 22, 2009

    The cake is fabulous (and no, I haven’t seen it yet, either), but the story about the unicorn is even better. Thanks for sharing M’s birthday with us!

  5. The cake is perfect! I love the unicorn magic. I didn’t know that unicorns could do that. They are very clever. Happy birthday ‘M’!

  6. Dad

     /  June 23, 2009

    Happy birthday M.
    Kate, what a lovely cake, so lovely that I’m getting Yerma to make me one for my un-birthday.

  7. Wonderful cake!!! I love the look on your little girls face blowing out the candles! So fun!

  8. That is awesome!!!! I think this would be even great to impress some adults! Thanks!

  9. Oh wow … 4 or 40, this cake would put a smile on anyone’s face! How clever of you!

  10. WOW! What a pretty cake and what a great technique! M is very lucky!

  11. Kate, happy B-day to your daughter! I loved her unicorn idea for the party:) Would have never thought about anything like that myself:)

    Your rainbow cake looks so beautiful. You did a fantastic job. Thank you for referring to my zebra cake. Cheers!

  12. Thanks, Rose 🙂

    I’m so pleased you like it, Julie – thanks for letting me know!

    Unicorns are very clever indeed, Melinda – it’s surprising how many things can be achieved with a little unicorn magic 😉

    Good luck with that one, Dad!

    Thanks, Jen – she was certainly a very happy birthday girl!

    Funnily enough, Niki Theo, the parents were quite intrigued by the cake when they came to collect their daughters at the end of the party!

    That’s very kind of you, Little Teochew 🙂

    Thanks, evilcakelady 🙂

    And thank *you* for the recipe, Farida – it just goes to show that zebras don’t always have to be monochromatic!

  13. I, for one, had never seen anything like that before, and I think it’s wonderful! As the mother of a soon-to-be five year old daughter, I’m excited for the possibilities come birthday party time in August. However, as someone who only makes cakes about once every two years, I’d love to have the recipe for the batter you used. The cakes I make tend to have very runny batter and I don’t image that will work out so pretty (as you mention.)

    BTW, I’m pretty sure I found you through tastespotting. Love that site!

  14. TasteStopping

     /  June 24, 2009

    That is such a fantastic story to go along with a wonderful cake. I’m just as mesmerized as your small guests were! (Isn’t is wonderful when you can elicit that kind of response from the younger set?)

    Anyway, I found you on TasteSpotting and am writing to say that if you have any photos that aren’t accepted there, I’d love to publish them. Visit my new site (below), it’s a lot of fun! I hope you will consider it.


  15. Hi Kristi – Welcome to ‘A Merrier World’ 🙂
    I used Farida’s recipe for the batter, which you can find in her zebra cake post – http://www.azcookbook.com/zebra-cake/ . Instead of colouring half of the batter brown with cocoa though, I divided the batter into seven bowls and coloured the portions with rainbow colours. It’s not so very thick as a batter, but it does hold its shape well during baking.
    Good luck – I’d love to hear what your daughter thinks of her cake!

  16. I want a unicorn birthday party, and I’m twenty!!! Complete with magical rainbow cake of course. Thanks for that Something Awful link too–who woulda thought they had food forums?

  17. Liz

     /  June 24, 2009

    Wow, this is beautiful. I was planning to make these cupcakes http://www.bigredkitchen.com/2009/05/rainbow-cupcakes.html soon but now I might bake this cake for my own 21st birthday!

  18. Abby

     /  June 24, 2009

    This is brilliant!

    Can one use regular food coloring for this?
    I would imagine the colors wouldn’t come out as vibrant.

    If the answer is no, how much is/where can I find fondant paste dye?


    • I couldn’t find my red food paste dye when I made the cake, so I used my Supercook liquid red dye and the red layer seemed to turn out fine – I don’t remember the batter being noticeably any more runny. If you want to stick with the paste dyes (they do offer very vibrant colours for very little dye used), then the ones I use are by from the Wilton icing colours set. I’m not sure you’d find this in a supermarket, but I’ve certainly seen it in several specialist cake making/decorating shops.

      I hope that helps 🙂 .

  19. Wow, I’m thirty-something and *I* want that cake!

  20. Kaytie Marie

     /  June 25, 2009

    aww i’ve never heard of a rainbow cake before…too cute! 🙂

  21. Forrester McLeod

     /  June 25, 2009

    Wow! Okay! You win Birthday Mom of the Year!!! Big gold star on your forehead. You know she’ll be talking about this her whole life…


  22. chamblee54

     /  June 25, 2009

    I just got through re posting this with rainbow text.

  23. the elderflower man

     /  June 25, 2009

    that looks great, our daughter is 6 next month and is mad about unicorns and I think we might just have to try this one out.

  24. sisterrosie

     /  June 26, 2009

    I’ve been thinking about rainbow cake for a while – I saw some rainbow muffins, and now I think in technicolour. Thanks for the tip about pouring the batter! But, you know, I don’t have any 4 year olds to bake psychadelic cakes for…I may have to adopt some.
    Happy baking!

  25. My nieces have always been a fan of rainbow cupcakes, believing that the frosting is a tuff of clouds they bite into, but this whole unicorn story just totally warmed my heart. Great surprise for the birthday girl!

  26. Allison Holley

     /  June 27, 2009

    That is awesome, what a way to make the birthday girl and her friends feel special on such an important day!

  27. Jeannette

     /  June 30, 2009

    Hi Kate, We’ve just got back from holiday and I clicked on to your blog to see this lovely cake. What a great cake for a little one or a big one for that matter! Does M share her birthday with Tom? His was on the 22nd of June, we were away at the time so he hasn’t had a birthday cake yet, I wonder if he’d like a Unicorn cake…… LOL1

  28. Pure joy! I got a bolt of nostalgia/longing for my daughter to be little again so I could make this for her. What a delight!…and made with love, not Martha-esque overachievement, better still!

  29. Rosemarie Squeri

     /  July 3, 2009

    Hi, What a fantastic cake. Will try to make it some day. A little hint. There is a toy store at my local shopping center and I was in there a few days ago. They have lots of magical figures, dragons, knights in armor and festive horses, all kinds of fantastic figures. Can’t remember the brand name, but maybe it is on the internet. Boys may like the dragons, (I do too and I’m an old grandma). If anyone wants these and can’t find any, email me and I will get the brand name for you. Happy Baking.
    PS, my son is 30 and for his birthday, I got figures from the show, Heroes, which he loves. I hesitated doing something so childish but did it anyway. He was so amazed and delighted and now has some figures for a collection that he can sell in the future. All his friends got a kick out of it and when the candles were lit (not 30, of course) someone yelled “save the cheerleader, save the cake.” Heroes fans will understand.

  30. That is such a cute story- and gorgeous cake. What a precious little girl you have!

  31. I hope M doesn’t read your blog and find out the secret behind the Unicorn Magic Rainbow Cake. What fun–it made me smile to look at it and think how wide-eyed the kids must have been.

  32. Now that is one awesome cake, especially for a little girl. Nice job!

  33. Jane Dioguardi

     /  August 29, 2009

    I have been waiting impatiently for my grandson’s birthday to make a rainbow cake! My little buddy turned two today, and his party is tomorrow. I forgot to use the technique above for the top tier, so that will probably turn out looking tie-dyed–but I’ll remember to pour out the batters correctly on the top tier. Can’t wait to see how it turns out!

  34. steve

     /  September 15, 2009

    how many cake pans do you need for the rainbow cake? can you just use wilton coloring thanks steve

  35. I used one 9″x2″ round cake pan, Steve. For colouring the batter, I used the paste dyes from this Wilton icing colours set … is it the Wilton coloring you mean?

  36. What a great cake!

  37. susanne

     /  January 22, 2010

    Wow! i found this while looking for unicorn ideas for my daughter’s birthday party and it is perfect! Can’t wait to try it. what recipe do you use for buttercream icing?

    • I didn’t really use a recipe for this – I just melted some white chocolate and stirred it into some beaten butter, then added a bit of icing sugar to sweeten it enough to suit a 4-yr-old’s taste buds. I hope that helps – and that your daughter has a wonderful birthday!

  38. cyndy

     /  February 1, 2010

    I love love love this concept and this cake, especially for kid! I have a few questions:

    First, Farida just said to “oil” the pan. Did you grease and flour the bottom and add parchement and grease and flour over that and then leave the sides alone? Or did you grease and flour the whole pan or did you just grease the pan?

    Second, was the cake too tender? Was it difficult to move from cooling rack to board? I was thinking of doing this as a two layer deal. I get the bake even strips are out so a dome is to be expected.

    How as the sweetness of Farida’s cake?

    Will this cake hold the weight of fondant?

    Did you use oil? Or, did you use butter?

    Your help will be appreciated! I am thinking a white/ivory for a cake for the end of this week.


    • Hi Cyndy 🙂
      I greased the pan (including the sides), then added a circle of baking parchment to the bottom, greased that slightly and floured the whole pan. I don’t rememeber the cake being too tender at all – I had no trouble moving it from the cooling rack. I used sunflower oil.
      Yes, I think the cake would easily hold the weight of fondant – it held a significant amount of buttercream plus supported a unicorn and candles.

      If you have time to experiment, you could always try using your own favourite cake recipe for the basic batter, then colouring it and pouring it into the pans to give the rainbow effect. As far as the sweetness of Farida’s recipe goes – it entirely satisfied its audience of 4-year old girls, but their Mums all enjoyed a slice too!

      I hope that helps 🙂

  39. Rupa

     /  April 14, 2010

    My daughter is going to be turning 5 soon and wants a unicorn cake. And I thought the rainbow cake idea was a great idea. For the cake mixture you used Farida’s recipe. What cookbook was her recipe in? How long do I need to wait before adding the next color? Please email me soon because her birthday party is May.

  40. Rupa

     /  April 14, 2010

    Another question, since you made the cake mixture white did you omit the dark cocoa powder?

    • Hi Rupa 🙂

      I don’t know the source of Farida’s recipe, but you can easily find it on her blog at http://www.azcookbook.com/zebra-cake/ . Yes, I omitted the cocoa powder (ie. I completed steps 1-3 of Farida’s recipe, then divided my batter into 7 parts and coloured each of these a different colour of the rainbow). You don’t need to wait any time at all before pouring in the next colour. Each new colour pushes the preceding colour out a little further in the pan, so don’t try to spread each batter out to cover the base at all – it happens naturally. Just make sure that you aim for the centre of the pan when you pour in each colour.

      I hope that helps – good luck for your daughter’s birthday. It’s my son’s birthday in May too (he’ll be 3), but rainbows aren’t quite his thing! I have a feeling I’ll be investigating tractor cakes or digger cakes all too soon … yikes!

  41. Leona

     /  July 6, 2010

    Fabulous, I don’t have any grandkids yet, but I will be saving this one for birthdays when I do. THX so much.

  42. musical mommy

     /  October 17, 2010

    I borrowed your rainbow cake recipe. It was SOOO much fun to make. Super pretty. The instructions were clear and – it worked. The birthday girl and all her guests loved it (and so did the mommies). Thank you for your post and all the smiles it made.

  43. Bilqis

     /  October 26, 2010

    fabulous cake! i will definitely try it for my nephew’s birthday. thx for the inspiration 🙂

  44. hi, this is just SO stunning, I have no words. I adore the story about the unicorn as much as I love the beautiful rainbow cake. I will be making this for my DD turning 5 in April. It’s such a relief to see something and know immediately that it is the cake I need to make! I usually spend ages trying to decide what to do, but as soon as I saw this I knew it was the one. Thank you SO much for sharing this, it is divine.

  45. Thanks so much for this post! I fell in love with your cake when I Googled it. If you would like to see a photo of our Unicorn Rainbow Cake, please visit my blog: http://zengarden1-11.blogspot.com/2011/05/magic-is-afoot.html

    • Happy Birthday to your daughter, Holly – it looks like she had a wonderful party … and cake! Thanks for letting me know about it 🙂

  46. That is amazing and I want to try it for the girls’ birthdays!

  47. you are the most magical of mommies! xox rose

  48. Made it for Anna’s 3rd birthday and it went down a treat thank you!

    • Hi Karen – I’m really pleased you (and Anna!) liked the cake. Thanks for letting me know. I can’t believe she’s three years old already. Where did all that time go …?!

  49. Jo Johnson

     /  October 20, 2013

    Hello Kate

    Your sister Lucy pointed me in the direction of your blog after I remembered seeing a post about the rainbow cake before. I tried it last week for my daughter’s 5th birthday party, as well as the zebra cake version you pointed to. They were both brilliant – easy to do, and extremely impressive given the comments I got back from children and parents alike. One child said “wow, that’s the most amazing cake I’ve ever seen!” 🙂 Thanks for sharing the recipe and also the photos which I found useful. One thing I’d say to others trying it is that it was tricky to get the paste colours to blend into the cake mixture without first dissolving them in a tiny amount of hot water. And second, that I found the colours to be much brighter once cooked!! Anyway, I’m sure I’ll be making these cakes again.


    • Hi Jo – Sorry I missed your comment (my spam filters work too enthusiastically sometimes …). I’m pleased your cakes were so successful. And thanks too for sharing your tips on the colouring 🙂

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