Preheat oven to 425°F. Spray two 6-cavity doughnut pans with non-stick cooking spray.
In a medium bowl, whisk together the flour, granulated sugar, baking powder, cinnamon, nutmeg, and salt.
In a small bowl, whisk together the buttermilk, eggs, vegetable oil and vanilla extract.
Add the wet ingredients to the dry mixture and gently stir together until just combined.
Divide the batter into the prepared donut pans, filling almost full.
Bake for 7-9 minutes or until the tops spring back when lightly pressed.
In a small bowl, mix together the cinnamon-sugar.
As soon as the donuts are cooled enough to handle (but still warm), remove from pan and dip in cinnamon-sugar. Set on a wire rack to cool.