Ingredients
2 1/2 cups (285g) cake flour, 2 1/2 teaspoons baking powder, 1/2 teaspoon salt, 1 cup (2 sticks; 230g) unsalted butter
1 3/4 cups (350g) granulated sugar, 4 large egg yolks, 2 teaspoons pure vanilla extract, 1 cup (240ml) buttermilk, 2 large egg whites, 1/8 teaspoon cream of tartar
Instructions
Preheat oven to 350 degrees F (175 degrees C). Grease and flour two 9-inch round cake pans. In a medium bowl, whisk together the flour, baking powder, and salt.
In a large bowl, cream together the butter and sugar until light and fluffy. Beat in the egg yolks one at a time, then stir in the vanilla and buttermilk.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.
In a separate bowl, beat the egg whites and cream of tartar until stiff peaks form. Gently fold the egg whites into the batter.
Divide the batter evenly between the prepared cake pans. Bake for 27-31 minutes, or until a toothpick inserted into the center comes out clean.
Let the cakes cool in the pans for 10 minutes before inverting them onto wire racks to cool completely. Frost the cooled cakes with your favorite frosting.
For a richer flavor, use dark brown sugar instead of granulated sugar. For a more moist cake, add 1/2 cup sour cream to the batter.
To make a vanilla cake, omit the rum and add 1 teaspoon vanilla extract. To make a chocolate cake, add 1/2 cup unsweetened cocoa powder to the dry ingredients.