Carefully separate egg yolks and whites into 2 separate bowls, making sure that no yolks are in with the whites. Beat egg whites using a whisk until white and fluffy then set aside.
Add milk and melted butter to bowl containing egg yolks then whisk to combine. Add sugar, salt and vanilla then stir until dissolved.
Sift flour, baking soda and cinnamon over milk mixture then stir just until smooth. Fold in beaten egg whites until completely combined and no streaks of egg whites remain. Set batter aside to rest for about 10 minutes while you preheat the waffle iron.
Spray waffle iron lightly with non-stick spray then add batter to hot waffle iron. Cook until golden brown and crispy. Serve hot from the waffle iron with any of your favorite accompaniments.
Notes
This batter is easily made ahead and stored in the refrigerator overnight so you can get a jump on breakfast!