Heat a heavy nonstick skillet over medium high heat. Saute ground beef and onion 5 minutes, stirring to break up meat, until browned. Discard excess fat.
Stir in soup, water, macaroni and salt and pepper to taste. Bring to a boil, stirring frequently. Reduce heat to low, cover partially, and simmer about 8 minutes, or until macaroni is just tender.
Stir in corn and transfer to a lightly buttered casserole. Cover tightly and bake 15 minutes. Remove cover and sprinkle with Cheddar cheese. Bake about 15 minutes longer, uncovered, until bubbly and cheese is melted.