I know there are a million rainbow cakes out in Internet-land, so I thought I’d add mine to the melee. Mini Minx turned 3 today and had asked for a ‘weather cake’ with the sky, the sun, clouds, rain, snowflakes and a rainbow. Eep! Luckily I remembered the brilliant rainbow cake my friend Tracy had made her wee daughter last month, and the tips she’d given me about colourings. She’d kept the inside a surprise, and I thought that was a fantastic idea. If you’ve seen the video of little Mini cutting her cake and her reaction at discovering the rainbow inside, then you’ll see why I think most of the impact of this pretty cake is from keeping the inside a secret! So try to make it when no-one’s around…
It was actually pretty easy to do, and from start to finish took me a single evening. Call it 4 hours, absolute tops, including baking and cooling times. But I was doing other things at the same time too, like cook dinner, eat, get kids to bed, etc. So really not too arduous.
OK, first of all, assemble all your kit. You don’t need it all, but it certainly made things much easier for me:
- I use disposable paper cases because I’m rubbish at greasing and lining baking tins. They’re like massive cupcake cases. If you have them, 15cm diameter cases and tins would be ideal, but I used 18cm cases (in 20cm tins)
- 2 cake tins. Small ones. 15cm diameter would be spot-on.
- food processor or mixer. I used one with a whirly blade rather than a proper Kenwood mixer thing. It’ll be fine!
- wooden spoon
- small mixing bowl
- electronic weighing scales
Here are the ingredients for the sponge cake bit:
- 6 large eggs
- about 300g self-raising flour
- about 300g softened butter
- about 300g castor sugar
- vanilla extract
- food colouring. Gel colourings give you brighter results than the liquid food colouring bottles you get in supermarkets, but they’ll be fine, too.
Here’s my basic sponge recipe, which makes 2 layers:
- Put the food processor base onto a set of scales. Crack 2 large eggs into it. Note the weight (should be around about 100g or so).
- Add that same weight of castor sugar into the base.
- Add that same weight of butter, and also of self-raising flour.
- Whizz until it’s all processed.
Right! Let’s begin!
Preheat the oven to 190degC. Make up a batch of sponge recipe. Using the spatula, put about half into your mixing bowl. Don’t stress about being exact, just do it by eye. I say use the spatula because when you’re working with small amounts of sponge mixture, leaving a few tablespoons of mix on the sides of the food processor base is a real waste!
Add food colouring and a 1/4 teaspoon of vanilla extract. Mix with your wooden spoon. It’s up to you how much food colouring you use: I used a half teaspoon for each layer. Some folk prefer a more subtle effect… Scrape the mix into one of the cake tins and smooth it to the edges and so it’s fairly flat.
Scrape the other half of mix into the bowl (it’s up to you if you want to wash it out first or not – I didn’t bother*), add a 1/4 teaspoon of vanilla extract and 1/2 teaspoon of gel food colouring, mix, and put that in the other cake tin. Bake the 2 layers for 15 – 20 mins in an oven at 190degC. When they’re cooked (skewer comes out clean / bounces back when you press it lightly), leave them in the tins for 10 mins to cool, then take them out onto a wire rack to cool properly (still in their paper cases) and crack on with the next 2 layers. Repeat for the last 2 layers.
* I didn’t bother being too pedantic about stopping the colours mixing. I made the blue then the purple layers; the yellow then the green layers; and the red followed by the orange layers.
Now to construct your cake! It looks amazing if it’s layered with buttercream, but I think my gallbladder would complain a bit (!). So I spread some apricot jam between each layer. I didn’t bother heating it first because I’m not sure why you’d do that! Then while I sorted out the icing, I put the base of the (now cold) sandwich baking tin on the top, and put a weight on that (the big old mixing bowl) to gently compress the layers.
I made a buttercream with 100g butter, 225g icing sugar and about a tablespoon of milk. I blobbed it over the sides and used a spatula to smooth it around and over the top. That was about right – not too thick and not too skimpy.
Icing: I used a 1kg pack of ready-to-roll shop-bought icing. I guess it’s like fondant icing? I added a tiny blob of the blue gel food colouring and kneaded it into about 700g of the icing with a dough hook (I was too scared of the mess it might make of my fingers to do it by hand…). It didn’t take long to spread through the icing till it was a beautiful sky-blue. I rolled it out and draped it over the cake. I should have spent longer smoothing it over the cake, but tbh just plopped it on, squashed it around, and gave the top a wee polish with the palm of my hand to make it gently gleam.
Decoration: I used yellow icing to make a sun. Just a round cutter and an ‘i’ cutter. I stuck it on with a pastry brush and water. The clouds were some of the 300g icing left over. They were flower shapes that I cut in half. I used el-cheapo writing icing to blob and drip on ‘rain’. The name was made of white icing with red gel colouring added. The aircraft was just modelled from off-cuts all mixed up. I used more writing icing to add ‘strings’ to turn the name into an aircraft’s flying banner, and a smile to the sun.
Ta da! You’re done.
One of the ladies (Emma Ringer) on my FB page said that she’d made a rainbow cake with lemon flavouring. That made me guffaw and really appeals to my sense of humour! If I ever make this again, I’ll maybe make each layer a different flavour: mint, almond, lemon, etc. If you use liquid flavourings, then you just add a bit at the same time as the food colouring, so it shouldn’t be too much extra hassle (though the mix of flavours could be boak-worthy…!)