3 1/2 cups all-purpose flour, sifted twice before measuring
2 teaspoons baking powder
1 cup (2 sticks) butter, softened
2 cups sugar
6 eggs
1 cup milk
1 teaspoon vanilla extract

Caramel Frosting:
3 cups firmly packed brown sugar
2 cups milk
4 tablespoons (1/2 stick) butter
2 teaspoons vanilla extract

Preheat oven to 325ºF. Butter 2 9-inch layer cake pans and line the bottoms with parchment or waxed paper. Butter the waxed paper. Sift the flour with the baking powder and set aside.

In a large mixing bowl, cream the butter until fluffy, then gradually add the sugar, beating until creamy. Add the eggs, one at a time, and beat in thoroughly. Add the flour mixture alternately with the milk, beginning and ending with the dry ingredients. Stir well after each addition, but do not overmix. Stir in the vanilla extract. Turn the batter into the prepared pans.

Bake until the tops of the layers spring back when lightly touched, about 35 minutes. When the cake is done, cool 10 minutes in the pans, then turn out onto cake racks to cool completely.

To make the frosting: Combine the brown sugar and milk in a large saucepan. Bring to a boil and cook, stirring constantly, to a soft-ball stage or 234 to 240° on a candy thermometer. Remove from the heat, add the butter and vanilla, and beat at high speed until thick enough to hold to the cake when spread. If the frosting becomes too thick, beat in a few drops of hot water. Spread the caramel frosting over one layer of the cake, top with the other layer and cover the top and sides of the entire cake with the remaining frosting.