Italian Sausage and Peppers with Penne

Penne pasta (12 oz)

Italian sausage links (1 lb)

Olive oil (1 tbsp)

Bell peppers (sliced, 2 (I used red and green))

Yellow onion (sliced, 1/2 small)

Marinara sauce (1 jar (25 oz))

Parmesan cheese (2 tbsp (optional for topping))