Preheat oven to 375°F (190°C).
Cook pasta until al dente, drain, and set aside.
In a skillet, sauté onion and garlic in olive oil until fragrant.
Add zucchini, mushrooms, and bell pepper. Cook until soft.
Add ground beef (optional) and brown fully.
Stir in marinara sauce, Italian seasoning, salt, and pepper. Simmer 5 minutes.
Combine pasta with sauce, ricotta, half the mozzarella, and Parmesan.
Transfer mixture to a greased baking dish and top with remaining mozzarella.
Bake for 25–30 minutes, until bubbly and golden.
Garnish with fresh basil before serving.