Recipe: Rainbow Cake

Caitlyn's Rainbow Cake

Caitlyn’s Rainbow Cake

This post should probably be labelled my “split personality” rainbow cake. Notice how one half is decorated with 100s and 1000s, and the other half in splotchy icing? Here’s the story behind it…

Caitlyn is smitten by Rainbow Fairy books at the moment. So her wish for a rainbow cake for her 7th birthday had to be granted. Her logic had everything to do with the number seven: 7 colours of the rainbow, 7 letters in her name, 7 letters in the word ‘rainbow’… Trust me, seven-year-olds have it all figured out!

This cake was meant to look spectacular! Pretty as a picture!! Beyond beautiful!!!
Instead, what I ended up with was this.

How NOT to decorate a rainbow cake

How NOT to decorate a rainbow cake

Don’t get me wrong – the CAKE was scrumptious. But decorating it was a DISASTER!

It was the evening before the party and everything was humming along just fine. I had already assembled the rainbow cake layers with buttercream icing earlier on in the day.
But then I ran short for the petal decoration outside.
So I whipped up another batch.
Haste really does make waste – the buttercream icing s-p-l-i-t.

Much Googling ensued.
“Aerate the icing by whipping it up again,” said one website.
“Stick the icing in the fridge,” said another.
Nothing worked.
My buttercream icing mocked me with its curdled graininess. The liquids had separated from the solids and refused to emulsify.
I persisted. I persevered.
I whipped and whisked until I had bulging biceps.
No luck.
At 11pm, I threw in the towel. And threw out all the icing.
Out came the 100s and 1000s.
I flung them onto the undecorated side of the cake in frustration. Of course, they danced all over my dining table and added to my woes.
My ego in tatters, I called it a night at 11:55pm.

The next morning, I told Caitlyn my sob story. And Caitlyn, being the darling that she is, said, “Don’t worry, mum. I think it looks lovely.”

rainbow ingredients

So here’s my recipe for Rainbow Cake. I’ll leave the decoration ideas up to you!
I used a basic Victorian sponge recipe where all the ingredients are of equal quantities. Your ingredients need to be at room temperature.
I used six disposable cake pans (19cm diameter). But if you do not have disposable cake pans or a large enough mixing bowl, you can halve the recipe and make the cake in two batches (2 batches x 3 cakes each time).

Ingredients for the cake batter:
600g unsalted butter
600g caster sugar
600g self-raising flour, sifted
12 eggs
600mL milk
1 tsp vanilla bean paste
Gel paste colours


Preheat oven to 170°C. Grease your baking pans.
Using a very large mixing bowl, cream together the butter and sugar until pale and fluffy. Add the eggs, two at a time, mixing between each addition. Add the vanilla bean paste. Add approx. 200mL of the milk, then 200g of the flour. Make sure you do not add all the milk, as you may not need all of it. Alternating between the flour and the milk, add them in little by little, mixing between each addition until the all flour is incorporated.

Rainbow cake batter

Rainbow cake batter

Divide this cake batter into six equal portions.
Some people do this by carefully weighing out each part. I did this by levelling out the dough in my mixing bowl and using my spatula to mark out six divisions.
Take six clean bowls and put one part of batter into each bowl.
To colour the batter, only use gel pastes. Ordinary food colour will not give you these vivid shades and adding too much colour will make your cake taste bitter.
Using a toothpick, add a tiny bit of gel colour to each bowl and mix.
Bake for 20-30 minutes or until golden brown.
I managed to bake all cakes at one go – three on the upper shelf of my oven and three on the lower one. You may need to rotate the pans or even swap shelves, depending on your oven.

last sliceButtercream icing
600g unsalted butter, softened
600g icing mixture
6 tbsp milk
Gel paste colours

Using an electric mixture, beat all ingredients together until fluffy. Do not colour the icing just yet!

To assemble:
Smear a bit of icing onto your cake stand or board. This will help the cake stay in place.

Rainbow layers all stacked up

Rainbow layers all stacked up

Place the first cake layer – violet – on this icing to stick to the bottom. Cover the top of the violet cake with a thin layer of icing. Add the next layer – blue – (we skipped indigo) over this. Cover this with a layer of icing. And so on, until you have all the colours of the rainbow: violet, blue, green, yellow, orange, red.

Now cover the outside with icing, filling any gaps between the cake layers.
Choose the way you want to decorate the outside.
Smarties, M&Ms, lollies and coloured sprinkles are a safe bet.
Or, you could Google “rainbow petal cake” and try to do what I had in mind – and failed miserably!

rainbow family

Thank God for small mercies! Once the cake was cut, it looked sensational inside and tasted delicious. The birthday girl was in 7th heaven!

So tell me, have you had any baking bungles or kitchen catastrophes? If you had to choose, what’s your favourite cake? Do you remember any birthday cakes from your childhood?


2 responses to “Recipe: Rainbow Cake

  1. Pingback: Amigurumi | liaisonwithalison·

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