Simplified Two-Tin Rainbow Cake




Introduction: Simplified Two-Tin Rainbow Cake

About: I am a British chap living in China. Watch this space for half-baked ideas and dubious innovation. Often aided and abetted by my power-tool wielding daughter.

A simplified method of making a rainbow cake with just two baking tins.


I foolishly attempted to make a rainbow layer cake for my daughter's 7th birthday party recently.

It turned out OK (see second image). It was a 'good bake' as Paul Hollywood might say, but very laborious and as you can see the layers were not very even.

Then I discovered that I had to make a SECOND one that she could take to school.

I thought I would address some of the problems encountered with build no. 1 and share them here.


1. Too much equipment and too much time: 5 colours required 5 baking tins + 5 baking racks. Or in my case three baking tins used over two baking sessions.

2. Too fragile: many of the layers were too thin, difficult to extract from the baking tin (even when lined baking parchment) and hard to handle without coming apart.

3. Too sweet: so many people seem to find the traditional sponge recipe of equal measures butter, sugar and flour to be unpleasantly sweet and this sweetness tends to mask any other flavours.

The solution I developed in this instructible uses just two tins, one round of baking, and far less sugar.

Happy reading and happy baking!

Step 1: Make a Lot of Cake Batter

Prepare 2 x 24cm square baking tins by lining with baking parchment.

Then make a lot of cake batter.

This instructable is not really about how to make the cake batter. You can use your own favourite recipe, but I am sharing this recipe as I have found most sponge cake recipes to be unpleasantly sweet.

This is based on a madeira cake.


300g caster sugar

500g butter

700g plain flour

6 tsp baking powder

9 eggs

1 cup of milk

2 tsp vanilla essence

zest and juice of 3 lemons


Set oven to 180˚c

Cream the butter and sugar together for a few minutes in a large bowl (best with food processor)

Add the eggs one by one with a spoon of flour (sifted with the baking powder)

Add the rest of the liquid and then fold in the rest of the flour mixture.

Then divide into 4 bowls. It works out around 500g per bowl.

Add the colourants to each bowl.

This is a simplified rainbow cake for obvious reasons. There is only room for 4 colours.

I used Red Orange Yellow and Green.

I used Americolor gel colours. They seemed to work fine. You only need 3-4 drops per bowl. Don't worry if the colour looks a bit weak at this stage - it seems to intensify during cooking.

Spoon the mixture into the (lined) cake tins.

Try to get each mixture into one half of one tin.

Bake at 180˚c for around 40 minutes and check that a toothpick comes out clean.

Step 2: Cool, Trim & Cut Up Your Cakes

This is how my cakes turned out. Maybe slightly overdone, but they got a decent raise so they were thick enough to be handled without collapsing.

Let your cakes cool before cutting them up.

First even up the top surface so that it is reasonably flat.

Then chop the edges off square.

Then cut into 5 even blocks across the 2 colours (as shown).

By the time I had trimmed the cake, it was about 20cm square so each block was 4cm across.

Do the same to the other cake so you should end up with 10 blocks of roughly similar size.

Eat all the yummy offcuts.

Step 3: Cake Construction

The next step is to build the cake.

I used a buttercream mortar with an almond flavour:

225g Cream Cheese

450g Icing Sugar

50g Butter

4 tbsp almond powder (this is for making almond flavour drinks, you can use almond essence instead, but use about 1tsp instead - or any other flavour you like).

Method: Cream all ingredients together in food mixer.

Then take your first block and cement it to the other two blocks on the first level.

Don't forget to rotate the blocks so that they alternate and you get the full range of colours (see picture).

Continue adding the blocks in this pattern until you have a 9 block cake.

As you started with 10 blocks, you will have one left over. yum yum.

After building the cake, put it in the fridge for a couple of hours before trimming and adding the rest of the buttercream on the outside surface.

Step 4: Icing the Cake

Once the cake has come out of the fridge, trim it up square and cover with remainder of the buttercream mixture.

To ice the cake I used fondant icing, which I did not make myself.

I don't think anyone really likes to eat this, but it makes everything neat for a birthday cake.

I used a little of the blue colour in the icing to make a sky effect and then coloured some small offcuts with the colour gels.

To make the rainbow, I rolled five thin sausages of the coloured fondant, put them next to each otherr then curled into a rainbow shape, rolled it out, trimmed the ends and stuck it on the top with some more buttercream.

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    2 Discussions


    Question 2 years ago

    Have you ever put one colour on top of the other before cooking? Do you think they bleed together or just cook and maybe be a bit wobbly?

    Penolopy Bulnick
    Penolopy Bulnick

    4 years ago

    That is clever baking the two colors together!