Preheat and prep. Preheat your waffle iron and spray it with non-stick cooking spray.
Combine the dry ingredients. In a large mixing bowl, combine the flour, sugar, baking powder, and salt. Stir until thoroughly mixed.
Mix the wet ingredients. In a separate, medium bowl, whisk together the eggs, sourdough starter, melted butter, and milk until well combined.
Combine wet and dry. Pour the wet ingredients into the dry ingredients and gently stir until just combined. The batter will have some lumps but no dry spots.
Cook the waffles. Scoop about ½ cup of batter into the hot waffle iron, adjusting for the size of your iron. Cook until the waffles are golden brown.
Keep warm. Place cooked waffles on a cooling rack. If desired, keep them warm in a 200°F oven while you cook the remaining batter.
Serve. Serve with syrup, butter, whipped cream, or fresh berries.