Mix the pumpkin puree, egg, vegetable oil and brown sugar together until combined smoothly.
Whisk together the salt, flour, pumpkin pie spice and baking powder in a separate bowl.
Mix the dry ingredients with the wet ingredients just until combined. Let the mixture sit, covered with a towel for 10 minutes.
Spray a donut pan with nonstick cooking spray. Fill them ¾ of the way. Bake for 8-10 minutes, or until a toothpick comes out clean when inserted.
While the donuts are baking, whisk the sugar and cinnamon together. Set aside.
Let the donuts cool in the pan for about 10 minutes before tossing them in the cinnamon sugar.
Store leftover pumpkin puree in the freezer for the next time you have a craving for pumpkin donuts!These doughnuts are best enjoyed fresh, but can be stored for up to 5 days in a sealable plastic bag.If you want to freeze a batch, I recommend doing so plain. The cinnamon sugar can get soggy when thawed. Arrange the cooled doughnuts on a baking tray and freeze for 2 hours then place them in a freezer bag and store for up to 3 months. Thaw at room temperature.