I use Ateco food coloring, which can be found at http://www.atecousa.net
For the cake, make one box cake mix according to the directions on the box. Separate batter into 3 bowls with roughly about 1 cup of cake mix per bowl. Add desired food coloring to each bowl (purple, blue, green).
Bake cakes in round pans according to box instructions, but make sure you check the cake about 10 minutes before it’s supposed to be done. With less mix in each pan, they can cook faster.
Repeat for the remaining colors (red, orange, yellow). You will now have six layers of different colors.
For the frosting, mix together softened (room temperature) butter and softened (room temperature) cream cheese until well combined. Add vanilla. Combine. Slowly add in powder sugar.
(After the 5th cup of powdered sugar, taste the frosting and see if you would like it sweeter. I tend to use the full 6 cups, but some prefer the frosting less sweet.)
I try to first level each layer of cake with a large bread knife. For the rainbow cake especially, if all the layers are level, then they will evenly display when you cut into it.
Start with the PURPLE layer first. Put the purple layer on your cake stand or plate. Add enough frosting to cover the layer and some to spill over the edges, anywhere from 1/2 to one cup of frosting. Run the flat, straight side of a knife around the cake to smooth out the edges.
Add the BLUE layer of the cake. Put frosting in the middle, start spreading out frosting with the flat, straight side of a knife so that it covers the cake and falls out over the edges. Then run your knife around the outside edge of the cake to smooth out the sides.
Put the cake into the fridge for at least 2 hours or freeze for 1 hour.
Repeat with GREEN layer, then YELLOW layer.
Put cake into fridge for at least 2 hours or freeze for 1 hour.
Repeat with ORANGE layer, then RED layer.
Cover cake with frosting and run the flat, straight edge of a knife around the edges of the cake to smooth out the frosting.
(It was important for me to freeze the cake between layers for a couple reasons. The cake can get really heavy by the time you are adding the 4th, 5th, and 6th layers, but if it is somewhat frozen at this point, it will not get schmooshed or crushed. Also, it is much easier to frost the cake when it is solid, or not wobbling all over.)
Once you have finished frosting the cake, add any decorative touches or words that fit your occasion! Good luck!
(I set the skill level as difficult, but ONLY because of the time involved. Truly, anyone can do this, and do it well! It just takes a little patience. The end result is SOOO worth it!).”
There now, hop to it and post me some!