Preheat oven to 375°F (190°C) and line a 12-cup muffin tin with paper liners.

In a medium bowl, whisk together flour, baking powder, baking soda, salt, and cinnamon.

In another bowl, whisk sugar, melted butter, oil, egg, milk, and vanilla until well combined.

Add dry ingredients to the wet ingredients and gently fold until just combined—do not overmix.

Divide batter evenly among muffin cups, filling about 2/3 full.

Bake for 15–18 minutes or until a toothpick inserted into the center comes out clean.

In a small bowl, mix cinnamon and sugar for the topping.

While muffins are still warm, brush tops with melted butter and dip into the cinnamon-sugar mixture until coated.

Serve warm or at room temperature.