In a large mixing bowl, whisk together flour, sugar, baking powder, and salt until combined. In a separate bowl, mix milk, egg, melted butter, and vanilla until smooth. Combine wet and dry ingredients gently.

Preheat a non-stick skillet over medium heat for about 3 minutes and lightly grease it with cooking spray or melted butter.

Pour 1/4 cup of pancake batter onto the skillet for each pancake. Cook for 2-3 minutes until bubbles form, then flip and cook for another 1-2 minutes until golden brown.

Remove pancakes from skillet and sprinkle them generously with cinnamon sugar.

Repeat with remaining batter, keeping cooked pancakes warm on a plate covered with a kitchen towel.