Microwave butter for 30 second intervals until melted.
Whisk the egg whites until firm and form stiff peaks.
Mix the egg yolks, flours, sweetener, and baking powder.
Add the melted butter slowly, mixing to ensure it is a smooth consistency.
Add the milk and vanilla, mix well.
Gently fold spoons of the whisked egg whites into the yolk mixture. Try to keep as much of the air and fluffiness as possible.
Place enough of the waffle mixture into the warm waffle maker to make one waffle. Cook for approx 9 minutes, until golden.
Repeat until all the mixture has been used.