Place a rack in the center of your oven. Preheat oven to 425 degrees Fahrenheit 20 minutes before baking your muffins. Spray a 12-count muffin pan with baking spray and set aside.
In a large bowl, whisk together flour, baking powder, baking soda, salt, and spices.
In a medium bowl, whisk the wet ingredients and sugar together (eggs, brown sugar, pumpkin puree, butter, vanilla, and milk).
Pour the wet ingredients into the dry and mix until just combined. Your batter can have a few streaks of flour—be careful not to overmix at this stage. The batter will be very thick.
Fill your muffin cups about ¾ full. Sprinkle with turbinado sugar, if desired.
Bake the muffins for 5 minutes at 425. Then, reduce the temperature to 350 and continue baking for 14-18 additional minutes. Do not remove the muffins from the oven when you lower the temperature. Cool muffins in the pan for 5 minutes before removing to cool completely on a wire rack.
Muffins will remain fresh at room temperature for about 3 days. Transfer into the fridge in an airtight container for a week.