Preheat the oven to 400°F. Lightly grease 2 doughnut pans.
In a medium bowl, mix together the flour, salt, baking powder, cinnamon, and nutmeg. Stir to combine and set aside.
In a larger bowl, mix together the melted butter, oil, both sugars, egg, vanilla extract, and milk together. Stir until well-combined.
Pour in the flour mixture and mix until just combined. It is okay if there are a few lumps in the batter.
Evenly divide the batter into the doughnut wells.
Bake for about 12 – 14 minutes, or until they are golden brown and spring back when lightly touched.
Pour your cinnamon sugar mixture into a gallon bag and add the freshly baked doughnuts. Shake to coat. You may need to do this in batches, but work quickly as the doughnuts should still be very warm for the sugar to adhere.