Hi guys! It’s been eighteen months since I first made my simple Rainbow Cake here on Kerry Cooks, and in that time, Rainbow Cake’s have become even more crazily popular! BBC Good Food even featured one in their magazine (although it’s apparently not nearly as reliable as mine, judging by the reviews!).
If you’re thinking of making one, rest assured that Rainbow Cake can be easy and stress free. My recipe is a simple Victoria Sponge recipe that’s been adapted for bigger quantities. Once made, the batter is divided into six and the colouring added to give the bright rainbow layers. Dozens of people have made it with great success – check out the comments!
What type of food colouring should I use?
It’s really important that you use highly concentrated food colourings for this cake. These are normally called gel or paste colours. If you use an old fashioned liquid food colouring, the cake will taste horrible, and the colours will be insipid and weak (NOT a vivid rainbow!). The brands to go for are –
Yes – Sugarflair, Americolor, Wilton,
No – Dr Oetker (gel), Silver spoon (gel), any liquid colours whatsoever
If you have a specialist baking supplies shop nearby, you should be able to find gel colours for between £2.50 and £3 per pot. Failing that, you can buy sets of gel colours specifically for Rainbow Cake’s from eBay, and other online shops too – I recently bought some Americolor’s from Fair Cake.
I wrote a whole post on the subject of colouring cake sponge here.
Could I add other flavourings to my Rainbow Cake?
Yes! You could add a flavouring extract such as strawberry, almond, lemon, or even something more exotic like bubblegum.
What size cake tins did you use?
I used 6 inch disposable ‘flan cases’ to bake my cakes, which I bought from Wilkinson’s (UK). 6 inch tins is why my Rainbow Cake was so very tall! Depending on how tall you’d like your cake to be, 6, 7, or 8 disposable tins would work great – you’d just get either a taller or less tall cake. If you want a cake that’s bigger than 8 inches, you’ll need to scale up the recipe.
Lots of supermarkets and pound shops sell disposable cake tins too, so stock up whenever you see them. I even re-use mine, with a quick rinse and turn in the dishwasher.
How did you prep the tin foil tins before using?
The great things about disposable tins is that cakes seem to come out of them really easily. I simply prep by brushing melted butter around the bottom and sides of the tin (alternatively, you could use a cake release product). If your cake does get stuck, never fear, simply cut the tin foil sides of the tins at about every inch, and then flatten the sides – you should then be able to get a palette knife under the cake to loosen it.
How high will my layers rise?
The layers should be between 1 and 2 cm high, depending on what size tin you use. If your cakes don’t seem to have risen, troubleshoot by checking your self-raising flour – is it well within date? You should also try to get the cakes into the oven as soon as possible once the flour is added to the batter – not easy given that you’re dividing it into six and adding the colours, but work as quickly as you can.
Can you make the layers ahead?
Yes! In fact, if you can make them one or two days before you want to serve your cake, its ideal. When a cake is freshly baked, it’s very crumbly and difficult to stack. I recommend baking your cakes, wrapping them in clingfilm and popping them into the freezer, and then unwrapping and decorating the next day. It will make decorating so much easier, trust me!
Is it okay to leave the batter to sit while I bake three cakes?
6 disposable cake tins between 6 and 8 inches should fit easily into a normal sized oven with three shelves. If all of your tins can’t fit into the oven at once, there’s no harm letting half the mixture sit as long as it’s for a fairly short time (your cakes should be cooked in around 15 minutes). Cake mixture shouldn’t sit around for too long once the flour has been added, or the cake will become tough when cooked.
Does the frosting set firm?
The cream cheese frosting I recommend will set firm to the touch, although it may need some help from the fridge on a very hot day. When you’re decorating the cake, you’ll need to apply multiple layers of frosting, setting in the fridge.
I’m having problems with my cream cheese frosting, any advice?
Cream cheese frosting can be tricky – I wrote a whole post on how to get it right here.
Could I use another type of frosting to cream cheese frosting?
Of course! It’s your Rainbow Cake. You could also use a buttercream, or perhaps a chocolate frosting. It would be really nice to try one flavoured with strawberry or cherry extract too. If you’re not too confident with baking, you could even buy a pre-made frosting. Or you could even use jam.
Lots of Rainbow Cake recipes also recommend a Swiss Meringue Frosting, which is also white and popular due to not being overly sweet. If you’d like to give it a go, try this recipe by the reliable Annie’s Eats (you’ll want to double the quantities).
Could I use less sugar in the cream cheese frosting?
Definitely! Any frosting recipe is a guide – I normally add sugar 100g at a time until I’m happy with the sweetness.
How should I decorate my Rainbow Cake?
Excellent question! The answer is – however you want! I love a smooth, plain white finish (to which you can add rainbow coloured sprinkles if you want) which doesn’t give any hint to the cake inside, so that when it’s cut, its a magical surprise! This is also the most low-maintenance method of decorating your Rainbow Cake.
It is possible to cover your cream cheese frosting in fondant if you’d prefer too.
If you’d like to experiment with your decoration, check out my Rainbow Cake board on Pinterest for more inspiration! The rainbow ruffle and rainbow fondant heart cakes are especially awesome.
Do I need to use dowels to support my cake?
My cake didn’t have any support from dowels, and it held up just fine. Cream cheese frosting is very sticky and holds the cake together well. However, when you’re building your cake, I recommend sticking it to your cakeboard/serving plate with a little cream cheese frosting ‘glue’ and building it two layers at a time, popping it into the fridge for 20 minutes each time to allow the layers to set firm before adding more.
How should I transport my Rainbow Cake?
I transported mine in a large shopping bag (the big bag for life types from Marks and Spencer) and it did get a little knocked en route (on the BUS!). If your cake needs to be transported, I’d recommend a taller cake carrier (Lakeland and cake supplies shops do some lovely ones).
Do you have any other Rainbow Cake questions? Let me know what they are in the comments and I’ll do my best to help!