In a small skillet, saute onion in butter until tender; set aside. In a bowl, combine egg, corn, milk and hot pepper sauce; stir in muffin mix just until moistened. Pour into a greased 8-in. square baking pan.
Combine sour cream, 1/2 cup cheese, salt, dill and sauteed onion; spoon over batter. Sprinkle with remaining cheese. Bake at 425° for 30-35 minutes or until a toothpick inserted in the center comes out clean. Cut into squares; serve warm.