Beat sugar with butter until well blended. Add egg. Add milk, flour, baking powder, salt and cinnamon. Beat until combined (about 1-2 minutes).
Spray mini muffin pan with non-stick baking spray. Drop dough by tablespoon into each muffin cup. Bake in a 350 degree oven for about 13-15 minutes.
Remove and cool in pan about 10 minutes, then cool completely on wire rack.
When cool, dip each donut into the melted butter and roll in powdered sugar. Eat and enjoy!
Notes
Store powdered donut holes in an airtight container at room temperature. Enjoy within 5 days.
For an alternate topping, try rolling these donut holes in cinnamon-sugar instead of powdered sugar.
Spray the mini muffin tin with baking spray before adding the batter. This prevents them from sticking and makes it easy to remove donut holes from the pan.