Rainbow Cake How To...
My original plan was to have the inside of the cake rainbow colored and have it iced in all white. That's really the only way I've seen it done, and as you know by now, almost all of my ideas are borrowed from somewhere and tweaked to fit my needs. I was telling my mom my plan and she said she thought the cake would be prettier if I made the outside rainbow colored too. I didn't want to hear it. I didn't want to think about how I was going to do it. And I really didn't want to make 6 different colors of frosting. But I did...and I'm really happy about it. It turned out prettier than plain white and everyone was still super surprised when we cut into it!
Here's how I did it.
I made 3 white cakes, splitting each in half to give me 6 layers. Each half was tinted with Wilton gel food coloring and baked. Then I froze them. After the cakes were frozen I sliced about 1/3 off the top so that my cake wouldn't be too tall. I put them in the freezer until I was ready to frost them another day. Next I put a white buttercream crumb coat on top and in between the layers. And then I added several dowels to hold my cake together.
I mixed 6 colors of frosting and used disposable piping bags since there were so many colors. I used Wilton tip 12. It's just a big open circle. I squeezed a dollop of frosting and then squished it and swept my tip through it. I began with the purple and worked my way up the side of the cake.