Preheat oven to 375°F (190°C) and line a 12-cup muffin tin with paper liners.
In a bowl, whisk flour, sugar, baking powder, salt, and cinnamon.
In another bowl, whisk melted butter, milk, eggs, nutmeg, and vanilla.
Combine wet and dry ingredients, stirring until just mixed.
Divide batter evenly into the muffin cups and bake for 20-25 min, or until a toothpick comes out clean.
Dip warm muffin tops in cinnamon sugar mixture; bake 2-3 min for a crispier finish.