A beautiful rainbow cake to celebrate any kid’s birthday party! And prepared with one of my favourite chocolate cake recipes: mayonnaise cake. It might sound weird to put mayonnaise in a cake, but it makes sense when you think about the ingredients separately: nothing but eggs, and oil, as many other cakes. This chocolate cake is moist, tender and delightful. And really easy to make, so why don’t you give it a try?

{Rainbow cake}

Preparation time: 30 min

Cooking time: 45 min

Yield: 18



  • 1 1/4 cups mayonnaise
  • 1 cup sugar
  • 2 cups flour
  • 4 tbs unsweetened cocoa powder
  • 1 tbs baking powder
  • 1 cup water
  • 1 tsp powdered vanilla pod
  • Buttercream:

  • 1/2 cup milk
  • 1 cup confectioner’s sugar
  • 3 sticks butter, room temperature
  • Decoration:

  • 44 oz M&M or smarties (5 packets)
  • 2 cups pink, blue or white candy cotton


  1. First prepare the cake. Preheat oven to 350ºF and grease a 20-22 mold. Set aside. Put mayonnaise in a large bowl, add dry ingredients, and finally water. Beat on low speed until completely integrated. Pour cake mix on the mold, and bake for 40 minutes (it should not be completely dry, it is a moist cake)
  2. Once baked, let it cool on a wire rack. When completely cool, cut a circle out of the centre of the cake using an 7-8cm round cutter and cut the cake in half to form the rainbow shapes
  3. To prepare the buttercream, beat all ingredients on high speed until fluffy
  4. Using a spatula or palette knife, spread buttercream over the cakes, covering completely. Arrange M&Ms over the top of the ganache, with rainbow colours. Place candy cotton as clouds on the bottoms of the cake

  • Rainbow cake idea came from Raspberri Cupcakes
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