Preheat grill (or grill pan) to medium/high.
In a large bowl, mix together the sausage, pepper, garlic powder, oregano, and basil.
Divide the meat mixture into 8 equal portions and shape each portion into burger patties.
Grill the patties on a preheated grill (or grill pan) for approximately 7-8 minutes per side (cover for half of the cooking time).
Meanwhile, in a grill basket (or a large stovetop skillet), season and cook the green peppers and onions with the salt and olive oil until they are slightly wilted and no longer crunchy. Stirring occasionally.
Place the cheese on the burgers and cook just until the cheese has melted. Remove from the grill and keep warm.
Spread the softened butter on both sides of the buns and season with garlic powder to taste.
Place the buns (butter side down) on the grill, or skillet, and cook until they're browned and lightly crispy.
Place a burger on a bun, top with prepared warmed marinara sauce, and the sauteed green pepper and onions.