Preheat your oven to 350ºF (175ºC) and prepare the donut pan with non-stick cooking spray.

In a medium bowl, combine pumpkin puree, brown sugar, vegetable oil, and milk until smooth.

In another bowl, whisk flour, baking powder, pumpkin pie spice, cinnamon, nutmeg, and salt until well combined.

Fold the dry ingredients into the wet mixture until just combined; do not overmix.

Transfer the batter into a piping bag and fill each cavity of the donut pan halfway.

Bake for 15 to 16 minutes until donuts spring back when pressed and a toothpick comes out clean.

Cool in the pan for about 10 minutes, then invert onto a wire rack to cool completely.

Melt butter and dip the tops of the donuts into it, then roll in the cinnamon sugar mixture.