A normally multilayered [[cake]], usually around 6 layers, with each layer being a separate color to create a rainbow when put together.  This is most commonly done by using food dye in the batter for each cake layer, but some cakes instead use different colored frostings to distinguish the layers.

Not to be confused with the Italian-American rainbow cookie, a 3-layer sponge cake cookie that traditionally features the colors green, white and red after the Italian flag.
rainbow cake