Preheat your oven to 350°F (175°C) and grease your donut pan lightly with cooking spray or oil.
In a large mixing bowl, combine the pumpkin puree, brown sugar, and vegetable oil. Mix until well combined.
Add the eggs and milk to the mixture, stirring well to incorporate.
In another bowl, mix together the whole wheat flour, baking powder, pumpkin spice, and salt until fully combined.
Slowly add the dry ingredients to the wet ingredients, gently folding until just mixed. Be careful not to overmix!
Transfer the batter to a piping bag (or a zip-top bag with the corner snipped off) and pipe the batter into the donut pan, filling each cavity about two-thirds full.
Bake for 15-18 minutes until a toothpick inserted into a donut comes out clean. Allow to cool for about 5 minutes in the pan before transferring to a wire rack to cool completely.
While cooling, you can prepare a simple glaze or dust the donuts with powdered sugar before serving.