Prep the pan: Line a 12-cup muffin tin with paper liners. Preheat the oven to 425°F (220°C).
Mix dry ingredients: In a large bowl, whisk flour, both sugars, baking soda, baking powder, salt, and spices until no clumps remain.
Mix wet ingredients: In a separate bowl, whisk pumpkin purée, eggs, oil, milk, and vanilla until smooth.
Combine: Pour the wet mixture into the dry. Stir gently with a spatula until just combined. Stop when you no longer see dry flour. Fold in any add-ins.
Fill the cups: Divide the batter evenly among the 12 liners, filling each almost to the top.
Sprinkle with coarse sugar if using.
Bake high, then lower: Bake at 425°F (220°C) for 5 minutes to boost rise. Without opening the oven, reduce the temperature to 350°F (175°C) and bake 14–16 more minutes, until a toothpick comes out clean or with a few moist crumbs.
Cool: Let muffins cool in the pan for 5 minutes, then move to a rack. Enjoy warm or at room temperature.