Mix the dry ingredients: Whisk the almond flour, baking powder, salt, and sweetener in a medium bowl.
Mix the wet ingredients: In a large bowl, whisk the egg yolks, almond milk, vanilla extract, and melted butter until combined.
Whip the egg whites: Beat the egg whites with a stand or hand mixer until stiff peaks form.
Make the batter: Stir the dry ingredients into the wet ingredients until combined.
Fold in the egg whites: Gently fold the whipped egg whites into the batter with a spatula just until incorporated. Avoid overmixing so the batter stays light and airy.
Preheat the waffle maker: Heat your waffle iron according to the manufacturer's instructions.
Cook: Add about 3/4 cup batter to a Belgian waffle maker, or the amount recommended for your machine. Cook for 3–4 minutes, or until golden, the waffle releases easily, and the steam has slowed considerably.
Repeat with the remaining batter.
Video
Notes
Yield: This recipe makes about 3 large Belgian waffles. The exact number will vary with the size of your waffle maker.
Almond flour: Superfine blanched almond flour gives the waffles the smoothest texture. I don't recommend replacing it with coarse almond meal.
Don't skip whipping the egg whites: This is what gives the almond flour waffles their lighter, fluffier center.
Keep batches crisp: Place cooked waffles in a single layer on a wire rack in a 200°F oven while you finish the remaining batter.
Storage: Refrigerate cooled waffles in an airtight container for up to 3 days or freeze them for longer storage.
Reheating: A toaster or toaster oven works best for restoring the crisp exterior.
Make ahead: Cook the waffles before storing them rather than refrigerating the batter. The whipped egg whites lose volume as the batter sits.