Not to be confused with the English Angel Cake.
The Angel Food Cake is an American sponge cake. It's name comes from the fact that its airy lightness was said to be "food of the angels". It became popular in the early 19th century. They are popular for post-funeral meals. Potassium bitartrate, also known as cream of tartar, is used in this cake to stabilize the egg whites, increasing their heat tolerance and volume.