Rainbow Cake & Easy Decorating

First of all, a disclaimer:  I got the idea to make a rainbow cake from multiple sources online, primarily at Whisk Kid, and her excellent tutorial on the Martha Stewart Show.  Tons of people have done this before me, but I still wanted to post the pics.  It's MUCH easier than you might think!  I used white cake mix and pre-made white frosting, so there are really only a couple of extra steps.  And I don't have the patience to learn to write on a cake, so I came up with a simpler solution...

I departed from the recipe on the back of the box of cake mix in only a couple of ways.

First, I scooped the finished batter from the original bowl into 4 separate bowls, a half-cup at a time until all the batter from the original bowl was gone.  ("One for you, one for you, one for you, and one for you.")

Then, I added gel food coloring until I got the desired color saturation.  This won't work with regular liquid food coloring unless you're ok with very pale, pastel colors.

Next, I baked two round cake layers at a time (only because I had 2 pans), with parchment paper lining the bottom of each pan.  I had to cut the time on the cake mix box quite a bit--just keep checking til a toothpick comes out clean.

Then, I waited until all layers were COMPLETELY cool, and sliced off the rounded top part with a bread knife.  I frosted between each layer, frosted the outside, chilled the cake, then made a final layer of frosting.  I'm not exaggerating when I say that this required about 3 tubs of frosting!  I probably could have used less between the layers.  But oh, well.

Then for the decorating!  I have a fairly steady hand, but didn't feel like learning a new skill (cake decorating) late at night when I was making this cake.  My solution: printing out letters to my son's name, using a 1-inch circle punch, and taping them to long wood sticks (ours were skewers we had on hand but you can get these in the cake & cupcake decorating aisle at Michael's). That's it!