In a large bowl, whisk together flour, baking powder, cinnamon, salt, granulated sugar, and brown sugar. This helps distribute the baking powder and spices evenly throughout the batter.
In a separate bowl, mix the milk, melted butter, eggs, and vanilla extract. Stir until everything looks smooth and creamy. This mixture will help make your batter light and moist.
Pour the wet mixture into your dry ingredients and stir until just combined—don’t overmix. Fold in the diced apples and optional nuts gently, making sure they’re evenly distributed without deflating the batter.
Preheat your waffle iron and lightly grease it with oil or non-stick spray. Pour enough batter to cover the surface, close the lid, and cook for about 3–5 minutes until golden and crisp. Repeat with the rest of the batter.
While the waffles cook, mix powdered sugar, milk, and vanilla extract in a small bowl until smooth. Once the waffles are done and slightly cooled, dip the tops in the glaze and let the excess drip off.