Bring a large pot of water to a boil.

In a large sauté pan, cook red bell pepper, white onion, and garlic in olive oil for 3-4 minutes or until lightly browned. 

Add the sliced sausage and cook for 2 minutes. 

Optional to deglaze with white wine and reduce until dry. 

Add alfredo sauce and marinara sauce and season with salt and black pepper. 

Cook penne according to package instructions in boiling water. Drain and add to the sauce. 

Toss to combine penne and sauce completely. Divide among serving bowls, sprinkle with green onion and serve immediately.