In the bowl of a stand mixer, beat together the butter and sugars until light and fluffy. Mix in the pumpkin puree, then beat in the egg and vanilla until fully incorporated.
In a separate medium bowl, mix together the flour, baking powder, cinnamon and nutmeg.
Slowly mix in the dry ingredients to the wet ingredients until fully incorporated. Cover and chill the dough in the refrigerator for at least an hour.
Preheat the oven to 350°F. Line two baking sheets with parchment paper or silicone baking mats. Mix the coating ingredients together in a small bowl. Scoop 1 tablespoon dough balls and roll into the sugar mixture. Place the dough balls onto the prepared baking sheet, about 1-2 inches apart.
Bake in the preheated oven for 12-14 minutes, or until the edges are golden. Let cool on the baking sheets about 3 minutes, then transfer to a wire rack to cool completely.