1. In a mixing bowl, stir together flour, sugar, baking powder and salt.
2. Separately, beat egg yolks with sour cream and melted butter. In another bowl, beat whites until stiff peaks form.
3. Stir sour cream mixture into flour mixture just until all ingredients are moistened, then stir in egg whites.
4. Spoon onto a hot, prepared waffle iron and bake until golden brown. Serve topped with a dollop of sour cream and fresh fruit, hot applesauce or with butter and maple or fruit syrup.