Preheat oven to 375°F (190°C). Grease 18 regular muffin cups.

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

In a medium bowl, whisk together sugar, eggs, pumpkin puree, sour cream, milk, vegetable oil, and vanilla extract until well blended.

Add the egg mixture to the flour mixture and stir until just blended.

Divide batter equally among prepared muffin cups.

Sprinkle each muffin with turbinado sugar.

Bake for 24-28 minutes, or until a toothpick inserted into the center comes out clean.

Let cool in the muffin pans on a wire rack for 3 minutes.

Transfer muffins to the wire rack to cool completely.