Heat oven to 375°F. Line a 12-cup muffin pan with paper liners.
Whisk pumpkin, granulated sugar, brown sugar, eggs, oil, milk, and vanilla until smooth and glossy.
Combine flour, baking powder, baking soda, salt, pumpkin pie spice, and cinnamon in a separate bowl.
Stir dry ingredients into wet just until no dry streaks remain. Do not overmix.
Portion batter into liners, about 3/4 full. Sprinkle coarse sugar on top if using.
Bake 17–20 minutes, until tops spring back and a toothpick comes out clean.
Cool 5 minutes in the pan, then transfer muffins to a rack to finish cooling.