Preheat a waffle iron to medium-high. Stir the almond flour, sweetener, baking powder, and salt together in a bowl. Add the eggs, melted butter, and vanilla, then whisk until smooth.

Brush the hot iron with butter or spray with nonstick spray. Spoon about ¼ to ⅓ cup batter into the center, close the lid, and cook until deep golden, 3 to 4 minutes.

Stack the waffles on a plate, add fresh berries, and drizzle with sugar-free syrup. Serve right away.