This year, with time on my hands, I decided to challenge myself to make a rainbow cake for my daughter’s birthday. I’ve always been reluctant to make a rainbow cake as I thought it would be tricky & very time consuming  – it turned out to be far easier than I had anticipated and I think the boys will now want a rainbow cake for their next birthday’s.

I used this recipe which is inspired by a Nigella recipe. A friend recommend that I buy Wilton Food Colouring from Amazon – it’s important to get a good colour that doesn’t fade during cooking.  Also I would definitely recommend using 4 cake tins. I had 2 x 20cm tins and I borrowed 2 which was a good call as it meant as soon as 2 cakes were cooked the next 2 could go straight into the oven. I also cooked my cakes for about 14 minutes – the recipe suggests 20 minutes which would have burnt in my oven so I would recommend for the first batch of cakes keeping an eye on them as they cook as timings seem to vary.

The decorated cake!

For ease, I have included the recipe below….

Makes one huge rainbow cake (six 8″ layers)


For the cake:

500g plain flour
3 tsp baking powder
1 tsp bicarb of soda
400ml buttermilk (or 150g plain yoghurt mixed with 250ml milk)
3 tsp vanilla extract
250g soft unsalted butter
400g caster sugar
6 large eggs

For the icing:

500g butter
1-1.5kg icing sugar
2 tsp vanilla extract
2 tbsp milk


Preheat oven to Gas mark 4 / 180 C / 170 fan.

Sift together the flour, baking powder, bicarb and a pinch of salt into a bowl. In another bowl or jug, stir the vanilla into the buttermilk.

Cream the butter and sugar together in a large bowl or electric mixer, until light and fluffy. Add the eggs one at a time, beating for 30 seconds in between each egg. Once they’re all in, add alternating amounts of the dry ingredients and the buttermilk, mixing well each time.

Divide up the batter into six bowls, one for each colour. I weighed out 300g cake mixture per bowl. Using a cocktail stick and teaspoon and keeping all implements very clearly segregated, carefully add the food colouring to the mixture. Decent paste colour is ‘true’ – ie, the colour you make the batter will be the colour of the finished cake – which makes things easier.

Bake in round tins for 20 minutes or until a fork comes out clean. I only had two tins the same size, so I did three shifts in the oven – if you line the tins well enough you shouldn’t need to wash them each time.

Spread a generous splodge of buttercream between each layer, and then a thick layer on the top and around the outside. To avoid pulling half the cake away with the icing, spoon on big dollops and then gently join them up using a spatula or palette knife. Once you’ve got a solid carapace of icing you can start to smooth it over.

Decorate. We used chocolate M&M’s but if you search on Pinterest there are loads of great examples for inspiration!