In a mixing bowl, combine flour, sugar, baking powder, and a pinch of salt.
Add milk, melted butter, and egg. Mix to form a soft dough.
Lightly flour a surface and roll the dough to ½ inch thickness.
Use a donut cutter (or two round cutters) to shape donuts and holes.
Preheat the air fryer to 180°C (350°F) for 5 minutes.
Place donuts in the air fryer basket in a single layer (do not overcrowd).
Air fry for 6–8 minutes or until golden brown. Flip halfway if needed.
Remove and let donuts cool slightly.
Dip in glaze, coat with powdered sugar, or sprinkle cinnamon sugar. Serve warm.