Pound cake is a relative of butter cake. It's so called because it can be measured as a matter of proportion: a pound of butter, a pound of sugar, a pound of eggs, and a pound of flour. In some pound cake recipes, you'll see the eggs separated and the egg whites whipped and folded into the batter, to leaven it; in other recipes you'll find leaven's like baking soda and baking powder, bringing it well into the butter-cake fold. These cakes are usually very lightly flavored and served plain or topped with a simple glaze or water icing. A pound cake is usually baked in a loaf or Bundt pan. Many coffee cakes, sour cream cakes, and fruit crumb cakes are variations of pound cake.