Lightly grease a 9"x13" pan and preheat oven to 350 degrees Fahrenheit.
Cook pasta according to package directions, but add salt to the boiling water before you add the pasta. Cook and drain.
In a large skillet or dutch oven, cook diced yellow onion, diced green pepper, Italian sausage and minced garlic, crumbling and breaking the meat up as you go. Cook until sausage is no longer pink and peppers and onions are tender. Drain the grease.
Stir in Italian diced tomatoes, marinara sauce, and Italian seasoning.
Add drained pasta and toss to coat completely in the sauce.
Pour and spread into prepared pan, cover with foil and bake for 25 minutes.
Remove the foil, sprinkle with parmesan and mozzarella cheese mixture and return it to the oven to bake for 5 more minutes. Enjoy immediately.