Preheat a waffle iron according to manufacturer's instructions.

Combine flour, baking powder, baking soda, sugar, salt, and cinnamon in a bowl. Beat egg whites in a separate bowl with an electric mixer until stiff peaks form.

Whisk buttermilk, melted butter, egg yolks, and vanilla together in a medium bowl until well blended. Stir in flour mixture until combined, then fold in egg whites.

Spoon 1/3 of the batter onto the preheated waffle iron; cook until waffle is golden brown and the iron stops steaming, about 5 minutes. Repeat to cook remaining two waffles.