Preheat oven to 350 degrees F (175 degrees C). Grease and flour three 9-inch round cake pans.
In a medium bowl, stir together the flour, baking powder, baking soda and salt.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla.
Beat in the flour mixture alternately with the sour cream. Stir in the nuts, if desired. Divide the batter evenly among the prepared pans.
Bake for 25 to 30 minutes in the preheated oven, or until a toothpick inserted into the center of the cake comes out clean. Allow to cool for 10 minutes, then remove from the pans and cool completely.
Place one layer on a serving plate. Spread with the filling of your choice. Top with the second layer, spread with filling, and top with the third layer.
Dust with powdered sugar, if desired.
Interesting Facts
Angel cake is a type of sponge cake that originated in the United States.
The cake is made with little or no fat, relying instead on whipped egg whites for leavening.
The cake is often served with a variety of fillings and toppings such as whipped cream, fresh fruit, or a glaze.