Heat oven to 350°F. Line a 12-cup muffin pan with paper liners.
Whisk flour, baking powder, baking soda, salt, pumpkin pie spice, and cinnamon in a bowl.
In a separate bowl, whisk granulated sugar, brown sugar, and eggs until smooth and slightly thick.
Stir in pumpkin puree, oil, and vanilla until evenly combined.
Add dry ingredients to wet and mix just until no flour streaks remain. Stir in milk to loosen the batter.
Divide batter among liners, filling each about three-quarters full.
Bake 18–21 minutes, until a toothpick comes out clean. Cool 10 minutes, then transfer to a rack to cool completely.