Heat oil in a large heavy-bottom pot. Add onion and sauté for four minutes, or until softened. Add garlic and sauté for another 30 seconds. Add marinara sauce, vegetable broth, and Italian seasoning and bring to a boil.

Pour in the penne, stir well, and reduce heat to a simmer. Stir often to keep the pasta from sticking.

Cook for 20 minutes, or until the pasta is cooked and the sauce is reduced by half.

Add mozzarella and Parmesan cheese and stir to combine. Serve immediately.