How to make a rainbow cake:

There's really no big secret to it, except maybe that you should use Wilton's paste food colorings that you get at Michaels or cake decorating stores to get the deeper, brighter colors.

But I just followed the directions on One Charming Party.  They have some fabulous party ideas.

I ended up using almost 2 white cake mixes, each layer using a little over 1 cup of colored batter.  After they were baked, I shaved off any high parts to try to make each layer as flat as possible.  Then I used just good ole homemade butter frosting.

Then, if you want pretty slices, you need to use a clean, hot, wet knife for each cut.  Fill a glass with hot water to dip your knife into each time.  Works like a charm.

It might be fun to have a rainbow cake for St. Patrick's Day.  Hmmmm...........