Preheat waffle iron.

Combine dry ingredients in large bowl and whisk together.

In a large measuring cup (4-cup Pyrex) or medium bowl combine buttermilk, milk, egg yolks, butter, vanilla and orange zest, if using.

Whip the egg whites with hand mixer in medium bowl until soft peaks form.

Pour buttermilk mixture into flour mixture, gently combine until few streaks of flour remain. Do not over beat, batter will be lumpy. Gently fold in whipped egg whites.

Cook according to your waffle maker.