01 - Preheat oven to 375°F. Grease a standard donut pan with nonstick spray or butter thoroughly.
02 - In a large bowl, whisk together flour, sugar, baking powder, cinnamon, and salt until evenly distributed.
03 - In a separate bowl, whisk together milk, eggs, melted butter, and vanilla extract until fully incorporated.
04 - Pour wet ingredients into dry ingredients. Stir gently until just combined; avoid overmixing to keep donuts tender.
05 - Spoon or pipe batter into prepared donut pan cavities, filling each about 3/4 full to allow for rising.
06 - Bake for 10 to 12 minutes until lightly golden and a toothpick inserted comes out clean.
07 - Let donuts rest in pan for 3 minutes, then carefully transfer to a wire rack for coating.
08 - Combine sugar and cinnamon in a shallow bowl, mixing thoroughly for even coating.
09 - Brush each warm donut lightly with melted butter, then roll in cinnamon sugar mixture until completely coated.
10 - Serve immediately while warm, or allow to cool to room temperature before serving.