1. In a large bowl, whisk together melted butter, brown sugar, and granulated sugar.
2. Stir in the pumpkin puree, egg yolk, and vanilla until smooth.
3. In a separate bowl, mix the flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
4. Combine wet and dry ingredients until just mixed. Chill dough for at least 1 hour.
5. Preheat oven to 350°F. Line baking sheet with parchment.
6. Scoop dough into 1.5 tbsp balls and roll in cinnamon sugar mixture.
7. Place on baking sheet and flatten slightly with fingers.
8. Bake for 10–12 minutes until edges are set but centers look slightly soft.
9. Cool on pan for 5 mins, then transfer to wire rack.