Make Life all Sunshine and Rainbows with a DIY Rainbow Cake!

rainbow cake

Who doesn’t like cake? A soulless person, that’s who. And who on earth doesn’t like rainbows? Pretty much no one! What if you were to take two of the greatest things on this planet (cake and rainbows, that is) and combine their powers to create a cake so cheerful and magical that you swear you landed somewhere in the land of the unicorns? Well, guess what – you can make that happen when you create a rainbow cake!

Imagine it: your friend or family member is cutting out their very first slice of rainbow cake, fully expecting something more run-of-the-mill like vanilla, yellow, or chocolate cake when BAM! Rainbow. Now that’s what we call a pretty sweet surprise!

So how can you make your very own magical rainbow cake? Just follow the directions below to get started!

Cake ingredients list:
*2 boxes of your favorite vanilla cake mix
*2 cups of water
*1 cup of vegetable oil
*6 eggs
*2 packages of classic gel food colors

Frosting ingredients list:
*1 bag (2 lb) of powdered sugar
*1 cup of shortening
*1 cup of softened butter
*2 teaspoons of vanilla
*3 to 4 tablespoons of milk


  1. Heat the oven to 350 degrees and spray 3 8-inch round cake pans with cooking spray.
  2. In a large bowl, beat the cake mix, oil, water, and eggs with an electric mixer on low speed for 30 seconds. Switch to medium speed for 2 minutes, scraping the bowl once in a while. Finally, divide the batter evenly among 6 small bowls – this should be about 1 1/3 cups of batter each!
  3. Tint the batter in the 6 bowls with the different food colors. Make 1 bowl blue, 1 bowl green, 1 bowl yellow, 1 bowl red, 1 bowl purple (by combining red and blue coloring), and 1 bowl orange (by combining red and yellow coloring).
  4. Refrigerate 3 colors of batter until they’re ready to be baked. Pour the other 3 colors of batter into their own cake pans. We recommend starting with purple, blue, and green.
  5. Bake these 3 mini cakes for 18 to 20 minutes. The cake should spring back when touched lightly in the center and should pull away from the pan’s sides. Cool for 10 minutes. Remove the cakes from the pans to cooling racks and cool completely.
  6. Wash the cakes pans – bake and cool the remaining 3 cake layers.
  7. In a large bowl, beat shortening and butter with an electric mixer on medium speed until light yellow. Next, on low speed, gradually beat in powdered sugar, followed by vanilla. Add milk, 1 tablespoon at a time, then beat until the frosting is smooth. Beat on high speed until the frosting is light and fluffy.
  8. Once the cakes have all cooled, level them by trimming any rounded tops. Place the purple cake layer on a serving plate. Spread with frosting to within ¼ of an inch to the edge. Repeat with the order of colors: blue, green, yellow, orange, and red. Spread a light coat of frosting on top and the side of the cake. Frost your creation with the remainder of frosting and feel free to throw down some sprinkles to give it a festive look!


If this looks totally daunting to you, we understand. It sounds complicated, and yes, your kitchen will get messy, and you’ll have a lot of dirty dishes to deal with. Save yourself the grief by having yours made by McArthur’s. It’ll look and taste wonderful and won’t be seasoned with tears of frustration! Order yours today by calling us at (314) 894-0900.