We’ve seen some fabulous baking techniques before, but this one truly takes the cake!
Jenn, the author of Cookies, Cupcakes and Cardio, had seen dozens of different versions of this incredible Rainbow Cake prior to making it, so she wanted to put her own spin on the outside of the cake in order to set it apart from the others! To achieve something truly unique (and gorgeous), she uses the “petal” technique — and it’s simply beautiful! Not to mention, in the end it seems like something you could actually learn to do yourself, and totally impress your friends.
You’re going to dirty a lot of dishes with this cake, so get the dishwasher ready!
You will need at least 1.5 batches of a vanilla cake recipe. Divide the batter into 6 bowls, and colour each one a separate colour. Bake each coloured cake in the oven until baked and allow to cool.
Prepare your buttercream. You will need a lot of it! Leave some of it white for the layers between the cakes, and the divide the rest up into 6 bowls, and colour each separately.
Start at the base, with the purple cake, add white buttercream, smooth it out, and then add the blue cake layer. Repeat, alternating between cake layers and buttercream until the final red layer is at the top. The order of colours from bottom to top is purple, blue, green, yellow, orange, red. To do the petal technique, you will need a large round tip. If you have 6 of the same tip, it will save you some time, but since I only had one, I had to empty my piping bag and clean the tip each time I changed colour. To make the petal shape, squeeze the tip, allow it to grow into a circle, and then pull the bag away along the side of the cake, creating a petal look.
If you want a cake as large as the one that I made, you will need 1.5 amounts of the batter recipe linked below and at LEAST double the amount of the buttercream. If you are using a box mix, I would use two boxes (mixed according to the package) and only use about 1.5 amounts of the batter that is made.