Preheat and Prepare Muffin Tin: Preheat oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners.
Mix Dry Ingredients: In a medium bowl, whisk together flour, granulated sugar, baking powder, salt, and ground cinnamon.
Combine Wet Ingredients: In a large bowl, whisk together melted butter, milk, eggs, ground nutmeg, and vanilla extract until smooth.
Combine Wet and Dry Ingredients: Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined.
Fill Muffin Cups: Divide the batter evenly among the muffin cups, filling each about two-thirds full.
Bake: Bake for 20-25 minutes or until a toothpick inserted in the center comes out clean. Cool in the tin for 5 minutes, then transfer to a wire rack.
Coat in Cinnamon Sugar: In a shallow dish, mix ½ cup granulated sugar and 1 tablespoon ground cinnamon. Dip the tops of warm muffins in the mixture.
Crisp the Tops (Optional): Return muffins to the oven for 2-3 minutes to crisp the tops.