Preheat broiler. Cook gnocchi according to package directions; drain., Meanwhile, in a large cast-iron or other ovenproof skillet, cook beef and onion over medium heat until beef is no longer pink, 4-6 minutes, breaking meat into crumbles. Drain., Stir in half the bacon; add gnocchi, water, cream and ketchup. Bring to a boil. Cook and stir over medium heat until sauce has thickened, 3-4 minutes. Add salt and pepper. Sprinkle with cheese., Broil 3-4 in. from heat until cheese has melted, 1-2 minutes. Top with tomatoes, green onions and remaining bacon.