In a large bowl combine your buttermilk, melted butter, vanilla, and egg yolks.
In a separate bowl combine your flour, baking powder, salt and sugar
Add your dry ingredients to your wet ingredients.
In a stand mixer, whisk your egg whites on high speed until they become fluffy and form soft peeks.
Fold your egg whites into your batter. Do not whisk or mix.
Using a waffle maker cook your waffles.
Mix your cinnamon and sugar together and in a separate bowl, melt your ¼ cup of butter.
Brush your waffles on both sides with the melted butter, then immediately and heavily sprinkle with the cinnamon sugar mixture.