Preheat the oven to 350°F (175°C) and prepare a muffin tin by greasing it or lining it with paper liners.

In a large bowl, whisk together all-purpose flour, granulated sugar, baking powder, salt, and ground cinnamon.

In another bowl, whisk together milk, eggs, melted butter, and vanilla extract until smooth.

Pour the wet mixture into the dry ingredients and gently fold until just combined.

Fill each muffin cup about three-quarters full with batter and sprinkle sugar on top if desired.

Bake for 18 to 20 minutes until golden brown; check with a toothpick for doneness.

Let cool for about 5 minutes before transferring muffins to a wire rack to cool completely.