OK, so here's the skinny (or not) on the rainbow cake from H's party. I can't remember where I first saw the idea, but it's been orbiting around the blogosphere for quite some time now.
You need two white cake mixes + needed ingredients (oil, egg, water, etc.).
Once mixed, you divide those two cake mixes among six bowls.
Note: this is not a ROYGBIV rainbow. I couldn't figure out how to differentiate between Blue, Indigo, and Violet using food dyes.
Add whatever edible thing you like to create the colors. I had aspired to use natural dyes--beet juice, pureed blackberries, etc., but didn't allow myself enough time to thoroughly research it.
So I used Wilton Gel Colors.
I used about 1/8 teaspoon of each color, and that was definitely enough to give vibrant color.
You will need up to six 8" round cake pans. I used four pans and didn't feel like I needed the other two. The baking time is so quick (15 minutes for me), I was able to bake, cool, wash, and refill without having it feel like a chore. I did use non-stick spray on each pan, then lined with parchment paper and sprayed again, so clean-up was easy anyway.
Finished cakes. Look at that color!
To assemble, make yourself a LOT of buttercream frosting.
I needed three batches of this basic recipe.
I added a little extra milk both to stretch the frosting as far as possible, and to make it easier to spread. I knew I'd be covering it with fondant, so I wasn't worried about how it looked.
Stack each layer in desired order, with a coat of frosting in between.
Then frost the top and sides, to give the fondant something to stick to.
Not so pretty! Fondant hides such (relatively) minor flaws.
If you're so inclined, here's the fondant recipe I use. It's a little involved, but nothing is difficult. And since it's made with marshmallows, it's really yummy.
You can still see a few lumps and bumps, but no one really minds except me.
Besides, it's the inside that counts.
