How To Make A Rainbow Cake

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rainbow birthday cake

Back in July, I made a rainbow cake for Dylan’s 1st birthday party. It took me a long time to decide what kind of cake I was going to make and I’d been looking forward to making him his first cake since pretty much before I got pregnant! A lot of research went into making the perfect cake – I spent hours Googling “how to make a rainbow cake” – and I was so pleased with how well it turned out. Lots of the cakes I bake look amazing in my imagination but I don’t manage to pull them off in real life. Thanks to my extra research, this one turned out even better than I’d hoped.

rainbow cake with with stripes inside

Inspiration

The starting point for my cake was this video from Cupcake Jemma. After watching this, I bought a few tools to make icing my cakes a little bit easier. A turntable, a couple of palette knives, a cake scraper and a cake leveller. I’ve used them for a few cakes now and they really help in getting the icing flat, especially on the sides of the cake. One thing that I don’t usually do is trim the cake before icing it and I was surprised at how much easier it made the whole process of icing. I’ve always avoided it as I hate waste but you actually take very little off the cake and anything that is trimmed away can be frozen and used to make cake pops later on.

The video includes directions on how to make the rainbow topper – it’s really very simple and looks great on top of the cake. One thing I did differently was to save the moulding icing that I trimmed from the ends of the rainbow. I used this to make little balls which I stuck around the base of the cake to edge it.

Extra Touches

I followed Jemma’s method of filling between the tiers and icing the sides of the cake but I decided to do the top a little differently by keeping it white which I think made the rainbow topper pop a little more. If you watch Jemma’s video on icing the sides, you will see that a lot of icing is scraped off when you smooth it down. I popped this leftover icing into a piping bag and piped ruffles around the edge of the cake to save it going to waste. I love the effect of the rainbow ruffles! Then I used some leftover moulding icing balls to randomly fill in any gaps and hide the transition between the red sides and white top.

rainbow cake

Fresh Flavours

I went for an orange and poppy seed cake with vanilla buttercream. One tip I have for icing a big cake like this is to make far to much icing. The worst thing when icing a cake is to get half way through and then realise that you might not have enough icing left. You either have to skimp on icing the rest of the cake or make a new batch and try to match the consistency and colour which can be difficult, not to mention time consuming. My recipe should give you more than enough icing for the four tiered cake. I froze the leftover buttercream and then used it to make cake pops so we got to enjoy the flavours of the cake again a few weeks later – win, win!

Rainbow Birthday Cake

Four tiers of orange and poppy seed sponge sandwiched together with rainbow coloured buttercream
Prep Time15 mins
Cook Time40 mins
Icing Time2 hrs
Course: Dessert
Keyword: birthday cake, cake, orange, poppy seed, rainbow, vanilla

Ingredients

For the cake

  • 400 g golden caster sugar
  • 400 g unsalted butter
  • 8 large eggs
  • 400 g self raising flour
  • 2 tsp baking powder
  • 2 oranges grated zest only
  • 2 tbsp poppy seeds
  • 4 tbsp milk

For the icing

  • 500 g unsalted butter at room temperature
  • 1600 g icing sugar sifted
  • 12 tsp milk
  • 4 tsp vanilla extract
  • food colourings see notes
  • 180 g modelling paste for the rainbow topper – I bought a white paste and then coloured it using food colouring

Instructions

For the cake

  • Pre-heat the oven to 190C/170C fan/gas mark 5. Grease and line two 20cm round cake tins. If you have four cake tins and they will all fit into your oven then by all means grease all four at once. I baked the first two tiers and after I turned them out I re-lined the tins to use for the last two tiers.
  • Beat together the golden caster sugar and butter until light and fluffy.
  • Add the eggs one at a time, beating well after each addition.
  • Mix in the orange zest, milk and poppy seeds.
  • Sift in the flour and baking powder and then gently fold into the mixture.
  • Divide evenly between the cake tins and then bake for 20 minutes (or until a skewer inserted into the centre comes out clean).

For the icing

  • Bο»Ώeat the butter for a few minutes until light and fluffy.
  • Gradually sift in the icing sugar and continue beating after each addition.
  • Mix in the vanilla extract and milk. You may need more or less milk depending on your room temperature so I would add a few teaspoons at a time to make sure your icing doesn't end up too runny. If it's too runny it will be hard to get a neat finish on the cake.
  • When you are happy with the consistency, split the icing into 7 bowls. Mix your food colourings into 6 of the bowls and then put each colour into a disposable piping bag. Snip the end off each bag – try to keep the openings the same size. Leave the remaining bowl of white icing for icing the top of the cake.
  • Have a look at Cupcake Jemma's video linked above to see how to ice the cake. I followed her method completely for the filling and sides of the cake. I decided to ice the top of my cake white and I used some of the scraped off icing from the sides to pipe swirls around the edge using a star nozzle. I also used some offcuts from the rainbow cake topper to edge the base of the cake and fill some gaps around the top edge.

Notes

I like to use the gel food colourings as they don’t change the consistency of the icing in the same way liquid colourings do. For this cake, I used red, yellow, green, blue and violet and I made the orange icing simply by mixing in red and yellow gel until I got the right colour.

For more cake recipes have a look at my Chocolate Orange Cake or my Honey and Lemon Cupcakes.

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