Preheat your oven to 375°F (190°C). Grease a 12-cup muffin tin or line with paper liners.
In a large mixing bowl, whisk together flour, sugar, baking powder, salt, cinnamon, and nutmeg.
In another bowl, whisk milk, melted butter, egg (or flax egg), and vanilla extract.
Gradually combine the wet ingredients with the dry ingredients, mixing until just combined.
Divide the batter evenly among the muffin cups, filling each about ¾ full.
Bake for 12-15 minutes, or until a toothpick inserted into the center comes out clean.
Let the muffins cool for 5 minutes in the tin before transferring them to a wire rack.
Melt the butter for the coating in a small bowl.
In another bowl, mix the sugar and cinnamon.
Brush each muffin lightly with melted butter.
Roll the muffins in the cinnamon sugar mixture until evenly coated.