1. Heat oven to 375 degrees F. Bring 1 inch water to boil in 4-quart saucepan over high heat. Add broccoli florets. Reduce heat to low; cover and simmer 2 minutes, stirring once. Drain and set aside.
2. In same saucepan, cook sausage and onion, stirring frequently, using spoon to break up sausage, until well browned. Stir in marinara sauce; heat through.
3. Toss marinara sauce, broccoli, mozzarella and Parmesan cheese with hot pasta. Spoon into shallow 2-1/2-quart baking dish; cover with foil. Bake 20 to 25 minutes or until cheese is melted. Makes 6 servings.