Katie Georgeson, from luxury cooker manufacturer Stoves, shares her tips for baking a stunning rainbow sponge cake.

Vibrant and joyful, a rainbow layer cake is the perfect showstopper for any occasion. While these impressive cakes take a fair amount of time and effort to make, it's all worth it when it's sliced and the colour is revealed. Read on for my top four baking and decorating tips.

Use top-quality food colouring

Vibrant colour is key to a successful rainbow cake, so it’s well worth investing in high-quality colouring. Gel varieties are better than liquid, as they're more highly concentrated, so you won’t need to use as much to get the same results (using lots of colouring can adversely affect the taste and consistency of the batter).

Bear in mind that you don’t need to buy every colour you'll use in the cake: secondary colours like green or purple can be mixed by hand. Take a look at this guide from Craftsy to learn more about mixing food colouring.



Bake evenly sized layers

Each layer of sponge must be evenly sized and perfectly baked if the cake is to hold its shape when the layers are stacked up. First, make sure that you have enough baking trays — these will all need to be the same diameter and depth. It may help to buy some disposable foil trays if you don’t want to invest in extra tins.

Next, you'll need to make sure that your oven is pre-heated to the temperature specified by the batter recipe. If you have a fanned oven, then you can bake your layers all at once, as the batter will rise well on any shelf. Bakers with conventional ovens can still cook all six layers in one batch, but it might help to rotate the tins halfway through baking.

If your cakes come out with a dome-shaped top, there's no need to panic — once cool, simply trim the top using a serrated bread knife.

Decorate your cake to perfection

Before you assemble and decorate your cake, consider freezing your sponge layers: this will reduce the risk of breakages and cracks, and help prevent the crumbs from ruining your icing.

A simple buttercream coating will look and taste beautiful, and the pale colour will provide a striking contrast against the vivid rainbow sponge. Apply a thin crumb layer all over the cake and let it set for an hour, then apply a thick final layer using a palette knife to get the top and sides as smooth as possible.

Add the finishing touches

Once the icing on your showstopper has set, you should be left with a blank canvas that you can decorate with a few finishing touches. You'll want to pick rainbow-coloured pieces that will contrast against the pale icing and match the colourful sponge layers. A simple centrepiece like this balloon topper or a rainbow candle will be all the decoration you need, and all you have to do is pop it on top of the cake.

Bear these tips in mind to create a beautiful rainbow cake that tastes every bit as good as it looks. 


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