Preheat your oven to 350 degrees and spray two mini donut pans with cooking spray. If you prefer, you can use a mini cupcake pan and make donut holes instead of donuts.
In a medium sized bowl whisk the flour, baking powder, cinnamon, nutmeg, ginger, cloves and salt together and set aside.
In a large bowl mix the pumpkin puree and brown sugar together, then add vegetable oil, vanilla, egg and buttermilk.
Combine ingredients together well, then slowly add the dry ingredients to the wet ingredients, whisking them together just until combined.
Fill mini donut hole pan sections about 3/4 full and bake for 10 minutes or until toothpick inserted into the center comes out clean.
While the donuts are baking, melt the butter to brush on top of the donuts and mix the sugar and cinnamon together in a small bowl.
Let the mini donuts cool for a couple of minutes and remove from the pan by tipping pan upside down over a cooling rack.
While donuts are still warm brush lightly with melted butter and dip individually into the cinnamon sugar mixture to coat.
Enjoy while warm! Donuts can be stored in a covered container for 2-3 days. I'd recommend covering them loosely with tinfoil so they don't retain moisture.