Preheat oven to 375°F (190°C) and grease a 12-cup muffin tin.
Whisk together 2 cups flour, 2 teaspoons baking powder, ½ teaspoon salt, and 1 teaspoon cinnamon.
In another bowl, mix ½ cup sugar, 1 egg, ½ cup melted butter, ¾ cup milk, and 1 teaspoon vanilla.
Combine wet and dry ingredients until just mixed.
Fill muffin cups two-thirds full and bake for 18–20 minutes.
While warm, brush each muffin with melted butter and roll in a mixture of ½ cup sugar and 2 teaspoons cinnamon.
Serve warm for a classic donut-like treat.
