Step 1Using an electric mixer, cream together the butter and sugar. Add the egg yolks, one at a time, until incorporated. Add the flour and buttermilk, a little at a time, alternating until each is incorporated. Stir in the salt and set aside.
Step 2In a separate bowl, whisk the egg whites to stiff peaks. Gently fold the whites into the batter, then gently fold in the baking powder until incorporated. The mixture will be thick and fluffy.
Step 3Bake according to the manufacturer's instructions for your waffle maker. Serve immediately.