Preheat the oven to 350F. Spray the donut pan with non-stick cooking spray and set aside.
In a large bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon and nutmeg. Set aside.
In a seperate, medium bowl, whisk together the egg, brown sugar, milk and yogurt (or sour cream). Then whisk in the melted butter and vanilla extract.
Pour the wet ingredients I to the dry and mix until just combined. Do not over mix. Spoon the batter into the prepared donut pan. Per the recipes recommendation, I placed the batter into a large Ziploc bag, cut a hole at one corner and piped the batter into the donut cavities. Fill no more than 3/4 of the way full with batter.
Bake for 8-10 minutes, or until just beginning to brown around the edges. Once done, let them sit in the pans for 2 minutes, then move the donuts into a wire rack to cool. This recipe makes 8 donuts but the pan only makes 6 at a time, so go ahead and pipe the remaining batter into the donut pans and repeat the baking process.
Allow to cool enough to handle before coating them.
To coat, combine the ground cinnamon and the sugar together in a shallow bowl. Brush the donuts with the melted butter using a pastry brush, then dip them in the cinnamon sugar mixture. You could do either just the top or all around the donut.
Store leftover donuts covered at room temperature for up to 2 days.