Heat a skillet to medium. Add a little oil. Olive oil or vegetable oil works fine.
Add the onion and green pepper to the skillet. Heat them until the onion is starting to become translucent. We like to keep a little "crunch" in the veggies, but do them to your preference.Add salt, pepper, and red peppers flakes to taste.
Add the sausage and cook until everything is heated throughout. That's it.
Notes
Use whatever sausage sounds good. We've used regular kielbasa, turkey kielbasa, and chicken sausage.