1. Preheat the oven to 425°. Spray a 12-cup muffin tin with cooking spray or line with liners.
2. Beat together the oil, eggs, sugar, pumpkin, spices, salt, and baking powder until smooth. Add the flour, stirring just until smooth. Let batter rest in the fridge for 15 minutes.
3. Divide batter evenly into muffin tin (fill each cup almost to the top, a hefty 3/4 full). Bake for 6 minutes and then reduce your oven temperature to 350° and bake for 16 to 18 more minutes or until a toothpick inserted comes out clean.
4. Let donut muffins cool almost completely then dip each muffin into the bowl with melted butter. Let excess butter drip off and then roll into the bowl of cinnamon sugar. Dip tops of the coated muffins in browned butter glaze, if desired.

Coating:

1. In a medium bowl, combine the sugar and cinnamon and mix until well combined.

Brown Butter Glaze:

1. Melt the butter in a small saucepan over low heat. Whisk constantly and continue cooking until golden, about 7- 8 minutes. Pour the butter into a small bowl and let cool for about 5 minutes. Whisk in the powdered sugar, milk and vanilla until smooth. Dip the donut tops in the glaze., if desired.