Preheat oven to 350°F. Lightly grease your donut pan with non-stick cooking spray.
In a small bowl, whisk together the flour, baking powder, salt, and nutmeg.
In a large bowl, combine granulated sugar, brown sugar, melted butter, sour cream, egg, and vanilla. Mix until smooth.
Add the dry ingredients to the wet and stir gently until just combined.
Transfer batter to a piping bag or Ziploc bag and pipe into donut pan cavities.
Bake for 12–14 minutes, or until golden brown and set. Cool slightly before glazing.
Let donuts cool slightly. For cinnamon sugar, dip each donut in melted butter and toss in the cinnamon-sugar mixture.
For vanilla glaze, whisk powdered sugar, milk, and vanilla until smooth. Dip each donut and let the glaze set on a wire rack.
These taste amazing drizzled with my Maple Glaze for a delicious fall flavored treat.