Bring large pot of water to boil. While waiting for water to boil, prep veggies. Heat deep skillet over medium heat and saute onion, 3 minutes. Stir in zucchini and cook another 3 minutes until onions and zucchini are tender. Salt water and cook tortellini according to package directions. Drain and set aside.
Stir tomatoes, salt and pepper into softened veggies. Simmer lightly for 5 minutes. Stir in cooked tortellini and parmesan cheese. Sprinkle top with mozzarella cheese and place under broiler until cheese is melted and bubbly. Serve hot.