In large nonstick skillet, cook ground beef and onion over medium-high heat until beef is thoroughly cooked, stirring frequently. Drain.
Add Alfredo sauce, water and ketchup; mix well. Bring to a boil, stirring occasionally. Add noodles; return to a boil. Cover; cook 5 minutes.
Add broccoli; cover and cook 8 to 10 minutes or until noodles and broccoli are tender, stirring occasionally. Sprinkle with cheese.