How to make a rainbow layer cake

Having children is the perfect excuse to let loose with all your baking dreams. From Women’s Weekly birthday cakes to Hungry Caterpillar inspired creations I love nothing better than an excuse to get out the food colouring.  For my baby boy’s first birthday I decided to take this one step further and attempt a rainbow layer cake for the first time. Food colouring overload!

Inside the rainbow layer cake

You’ve probably seen rainbow layer cakes on Instagram and Pinterest. Plain on the outside, cut them open and there’s a rainbow inside.  It’s a pretty spectacular “reveal” and sure to delight both big and little kids. 

All ready for a first birthday

It turns out making a rainbow layer cake isn’t actually that hard, just a bit time consuming to bake six separate cakes (bearing in mind this was the cheat’s way out and an authentic rainbow cake would have seven layers). 

Constructing the layer cake

I covered the cake with a buttercream icing because that’s my favourite for a creamy taste. It did a good job of holding all the layers together although gives a bit of a rustic appearance to the cake.  I topped the cake with some brightly coloured popcorn but curls of white chocolate would give a more grown up feel to this cake. 

Stacking up the layers
Rainbow layer cake
Cut this cake open to reveal rainbow layers inside.
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7352 calories
980 g
1944 g
343 g
102 g
206 g
2045 g
1248 g
593 g
13 g
111 g
Nutrition Facts
Serving Size
Amount Per Serving
Calories 7352
Calories from Fat 3021
% Daily Value *
Total Fat 343g
Saturated Fat 206g
Trans Fat 13g
Polyunsaturated Fat 19g
Monounsaturated Fat 92g
Cholesterol 1944mg
Sodium 1248mg
Total Carbohydrates 980g
Dietary Fiber 14g
Sugars 593g
Protein 102g
Vitamin A
Vitamin C
* Percent Daily Values are based on a 2,000 calorie diet. Your Daily Values may be higher or lower depending on your calorie needs.
  1. 250g butter, softened
  2. 2 tsps vanilla extract
  3. 2 cups caster sugar
  4. 6 eggs
  5. 4 cups plain flour, sifted
  6. 1 tsp baking powder,
  7. 1/2 tsp bicarbonate soda
  8. 1 cup milk
  9. Food colouring (the gel is better than the liquid).
  1. 125g of butter, softened
  2. 1½ cups of icing sugar
  3. 2 tbs of milk
  1. 1. Preheat oven to 160°C. Grease three 20cm round cake pans and line with baking paper.
  2. 2. Place the butter, vanilla, sugar, eggs, flour, baking powder, bicarbonate of soda and milk in the bowl of an electric mixer and beat on a low speed until combined.
  3. 3. Increase the speed to high and beat the mixture until it is just smooth.
  4. 4. Divide the mixture into six even portions. If you want to make sure your layers are evenly sized try weighing the mixture.
  5. 5. Add red food colouring to one bowl, yellow to another, blue to another, purple to another, orange to another and green to the final one. Mix the food colouring in well.
  6. 6. Pour one bowl into each cake tin. I did this in two batches as I only had three tins. Smooth surfaces.
  7. 7. Bake for 20 minutes or until cooked through. Stand cakes in pans for 5 minutes and then turn out onto wire racks to cool completely.
  8. 8. Wash and dry cake pans and grease and line with baking paper. Repeat with remaining cake mix and food colourings.
  1. 9. Beat the butter for about 10 mins in an electric mixer until it looks like whipped cream.
  2. 10. Add the icing sugar and milk in a little bit at a time. Keep the speed down low at first to avoid a cloud of icing sugar.
  1. 10. Place the first cake on a board or cake stand and top with a thin layer of frosting. Repeat with each cake and then cover the entire outside of the cake in frosting. Top with coloured popcorn, lollies or whatever you have to hand.
Gourmet Chick
A slice of rainbow cake action

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