Sponge cake is a cake based on flour (usually wheat flour), sugar, and eggs, and is sometimes leavened with baking powder. It has a firm, yet well aerated structure, similar to a sea sponge. In the United Kingdom a sponge cake may be produced by the batter method or the foam method, while in the US cakes made using the batter method are known as a butter or pound cake. Two common British batter method sponge cakes are the layered Victoria sponge cake and Madeira cake. Derivatives of the basic sponge cake idea include the American chiffon cake and the Latin American tres leches cake.