Preheat the waffle iron: Set it to medium-high.
A hot iron is key for crisp edges. Lightly brush with oil if your plates aren’t nonstick.
Mix dry ingredients: In a large bowl, whisk the flour, cornstarch, protein powder, sugar, baking powder, baking soda, and salt until well combined.
Whisk the wet ingredients: In a separate bowl, whisk the milk, eggs, melted butter or oil, vanilla, and lemon zest until smooth.
Combine gently: Pour the wet into the dry. Stir with a spatula just until no dry streaks remain. Do not overmix; a few small lumps are fine.
Rest the batter (5 minutes): This short rest hydrates the protein and flour, helping the waffles rise and crisp.
Cook the waffles: Pour batter into the preheated iron, about 1/2 to 3/4 cup depending on size.
Close the lid and cook until deeply golden and steam has mostly stopped, 3–5 minutes.
Hold them crisp: Place finished waffles on a wire rack set over a sheet pan. Keep in a 200°F (95°C) oven while you cook the rest.
Prep the berries: If using strawberries, hull and slice. Toss berries with a squeeze of lemon and a tiny pinch of sugar if they’re tart.
Serve: Top warm waffles with fresh berries.
Add a spoonful of Greek yogurt, a drizzle of maple syrup, or a dusting of powdered sugar if you like.