Cook the pasta according to the package directions, then drain.
Meanwhile, heat the oil in a large skillet over medium heat. Add the onion and garlic and cook, stirring, for 1 minute. Add the asparagus, carrot, and mushrooms and cook, stirring a few times, until the vegetables are crisp-tender, about 5 minutes. Add the salt and pepper, stir to coat.
Add tomatoes and cooked fettuccine to vegetable medley. Simmer for 2 minutes. Serve topped with mozzarella cheese.