In a large skillet, add onion and olive oil over medium heat. Add garlic; cook 1 minute longer. Stir in marinara sauce, diced tomatoes, zucchini, cooked turkey meatballs and Italian seasoning. Bring to a boil. Reduce heat; simmer, uncovered, 20 minutes.
Meanwhile, preheat oven to 350°. Cook pasta according to package directions; drain. If you are using Banza pasta, it takes just a few minutes to cook! It is really easy to overcook it! Add turkey meatballs and gently stir in tomatoes.
Spray cast iron skillet with cooking spray and transfer meatballs and sauce. Sprinkle with cheeses. Bake 15-20 minutes or until bubbly and heated through.
If you want a nice, crunchy layer of cheese, add to the broil for the last 3-5 minutes.