Preheat oven to 350°F. Grease two standard 6-cavity donut pans.
In a medium bowl, whisk together flour, baking powder, baking soda, cinnamon, pumpkin pie spice, ginger, nutmeg, and salt.
In a large bowl, whisk together pumpkin puree, brown sugar, granulated sugar, eggs, sour cream, melted butter, and vanilla until smooth.
Add the dry ingredients to the wet ingredients and gently fold until just combined. Don't overmix.
Spoon or pipe the batter into the prepared donut pans, filling each cavity about ¾ full.
Bake for 14–17 minutes, or until the tops spring back when lightly pressed and a toothpick comes out clean or with a few moist crumbs.
Let cool in the pans for 5–10 minutes, then transfer to a wire rack to cool completely.
Spread Nutella over the top of each cooled donut. Add sprinkles or chopped hazelnuts if desired.
Notes
Use pure pumpkin puree, not pumpkin pie filling.Full-fat sour cream gives the best texture.Silicone donut pans may require a few extra minutes of baking.Make sure donuts are completely cool before adding Nutella.Store in an airtight container at room temperature for up to 2 days.This revised batter has not yet been kitchen-tested; verify the baking time and yield before publishing.