Preheat oven to 350 degrees F. Coat a donut pan with nonstick cooking spray.
In a large bowl, combine pumpkin, oil, eggs and sugar. Mix well with an electric mixer on medium speed. Add remaining ingredients and mix on low until well combined. Fill each donut cavity to the top with batter.
Bake for 13-15 minutes, or until donuts spring back lightly when touched.
Meanwhile, combine sugar and cinnamon in a shallow dish. Melt butter in a separate bowl. Set aside.
Remove donuts from oven and let cool 5 minutes in pan. Place donuts on a cooling rack. Dip warm donuts in melted butter then into cinnamon-sugar mixture.