What is the key ingredient to making a cake?

A typical cake recipe calls for some type of fat (butter, margarine, shortening or oil) to be creamed together with sugar. Eggs are beaten into this mixture. Next, flour is sifted, and combined with baking powder, baking soda (or both) and salt. Then liquid, generally milk, is added to the batter alternately with the flour mixture. Flavorings are added at this time and the batter beaten gently until smooth. Most layer cakes are baked at 350º for about 24-35 min. depending on the type of pan(s) used. It is critical to success in almost all cakes to grease and flour the pans, the exception being angel food cake.