Preheat oven to 375°F Grease twelve 2 1/2-inch-diameter muffin cups.
Stir together flour, baking powder, salt and sugar in large bowl. Beat together egg, milk and melted butter in small bowl and pour over flour mixture. Stir to combine, but do not beat. Stir in cheese and pepperoni (if using).
Spoon batter into muffin tins, filling about 3/4 full. Bake 25 minutes or until muffins are high and golden. Remove to wire rack. Serve warm.