Preheat the oven to 350 degrees F. Mist donut pan with nonstick cooking spray and set aside.
In a medium-sized bowl whisk together the flour, sugar, baking soda, cinnamon, and salt. In a separate bowl, whisk together the sour cream, egg, vanilla, and oil; whisk until well-combined. Pour the wet ingredients into the dry and mix until fully incorporated.
Using a spoon, spread the batter evenly in each donut cavity, filling just over half full.
Bake for 13-15 minutes, until the donuts are golden brown and springy to touch. Remove from oven and let cool in the pan for 10-15 minutes, and then remove the donuts from the pan onto a cooling rack.
Meanwhile, combine the ingredients for the glaze in a shallow bowl. After the donuts have come to room temperature, dip each donut into the glaze. For best results, serve immediately.
Notes
*Nutrition information calculated based on amount of glaze used (2/3 cup powdered sugar, 2 tablespoons whole milk)