Chill a stainless-steel bowl and the whisk attachment of a hand blender in the freezer.
Preheat waffle iron on medium high heat.
In a bowl, whisk together the flour, baking powder, baking soda, salt, and sugar.
In a large bowl, whisk the egg yolks, then add in the buttermilk, butter and vanilla, whisk well to combine.
Add the flour mixture, a little at a time, to the egg mixture and continue whisking until the batter is smooth.
Remove the bowl and whisk from the freezer and add the egg whites to the bowl. Using an electric hand mixer, whisk on high until the egg whites form stiff peaks. Then, using a rubber spatula, gently fold in the egg whites into the batter. Cover the batter with plastic wrap and let sit at room temperature for 30 minutes.
Lightly spray or brush the waffle iron with oil. Then spoon batter into the middle of each well of the waffle iron and close the lid.
Cook the waffle until golden brown and slightly crisp, about 4-5 minutes.
Remove the waffles to a cooling rack placed on a baking sheet and keep warm in a 200F oven.
Repeat process: oil, batter, cook… until all the batter is done.