Preheat the oven to 350°F and spray doughnut pans with baking spray with flour.
In a large bowl, sift together flour, sugar, baking powder, cinnamon, and salt.
In a small bowl, whisk together egg, milk, melted butter, and vanilla.
Stir the wet mixture into the dry mixture, don’t over-mix.
Spoon batter into prepared baking trays, filling each doughnut space 1/3 full.
Bake for 17 minutes or until a toothpick comes out clean. Cool for 5 minutes.
While the doughnuts cool on the rack, melt butter in the microwave and make cinnamon sugar mixture.
Dip the top of the doughnut in butter and sprinkle with cinnamon sugar mixture.
Serve immediately!