Place the beef in a medium-sized pot and set over medium heat. Cook, stirring to break up the meat, until the beef is cooked through, about 5 minutes. Meanwhile, bring a large pot of lightly salted water to boil. When the meat is cooked, drain away the excess fat. Add the pasta sauce to the pan. Simmer 10 minutes. While that occurs, cook the pasta in the boiling water until just tender, about 8 minutes. Place the oven rack 6 inch beneath the broiler; preheat the broiler. When the pasta is cooked, drain well and divide among 4 heatproof bowls. Top with the meat sauce and sprinkle with an equal amount of the cheese. Broil the pasta 1 to 2 minutes, until the cheese is melted and golden brown.