Mix sweet paprika, brown sugar, onion flakes, salt, pepper, cayenne, garlic powder, and mustard powder in a bowl.
3 Tablespoons sweet paprika, 2 Tablespoons brown sugar, 2 teaspoons onion flakes, 1½ teaspoons salt, 1½ teaspoons cayenne, 1 teaspoon garlic powder, 1 teaspoon mustard powder, ½ teaspoon ground black pepper