How to Make a Fondant Rainbow Cake

by Tonya Staab
Published: Last Updated on

Whether you are hosting a rainbow party, or a St. Patrick’s Day party for kids, this easy fondant rainbow cake will be a hit.

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St. Patrick’s Day is nearing. Not that I need a reason to bake, but I thought it would be a great opportunity to make a rainbow cake for the kids. Of course, it will be well and truly eaten by St. Patrick’s Day.

half circle cake decorated to look like a rainbow cake

Rainbow Cake


  • Butter and flour, for pan
  • 1 box of your favorite cake mix
  • 1 can vanilla frosting
  • White fondant
  • Food dye – purple, pink, yellow, red, orange, green, and blue
  • Rainbow sprinkles
  • Gold foil-covered coins


Bake your favorite cake in a 9″ round pan using the package instructions.

Once the cake is cooled, cut it in half, so you end up with two semi-circles. Spread a thin layer of frosting on one side, and then put the other side on top.

Put a piece of wax or parchment paper underneath the cake and draw around it. Remove the parchment paper and then measure and sketch exactly how the rainbow should look.

Turn the cake over so that it’s in a rainbow shape and spread frosting over the front, back, and along the top.

Break off pieces of fondant, and using gloves, add food dye to each ball until your fondant is the desired color.

fondant balls that have been colored and then rolled out to make a rainbow cake
Fondant being made for a rainbow cake.

Tip: Wrap each colored ball in cling wrap until you are ready to use it. Fondant will become hard and dry quickly if you don’t do this.

Roll out one ball of fondant at a time starting with the blue. Using a sharp knife, cut the fondant according to the measurements you did earlier. Start with the blue fondant and work your way up the rainbow. Attach each piece of fondant to the icing across the front of the cake.

Spread rainbow sprinkles along the top of the cake.

You can use Wilton piping tips to create clouds or grass, and then add St. Patrick’s Day items such as a pot of gold and leprechaun if you like.

More rainbow food and crafts

Are you looking for more fun rainbow food and craft ideas? Take a look at these:

Please pin this post for later:

fondant rainbow cake pinterest

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Christina @Revupthepassion March 12, 2011 - 10:07 am

What a cute cake I’m my kids would love it I just might have to make this. Thanks for sharing!

Monica March 23, 2011 - 8:46 am

Love this! 🙂 I’m going to try fondant on my next cake… thanks for the info on how to do it!

Tonya Staab March 25, 2011 - 10:24 am

Thanks Monica, make sure you show me pictures if you do it :).  I miss you by the way.

Reply June 9, 2017 - 12:45 am

Yesterday there was a party in my family, we made this cake. It was very awesome!!!! Everobody praised of this cake.
Same Cake is also given on :


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