1 tablespoon olive oil
1 onion, thinly sliced
1 red bell pepper, cored and thinly sliced
1 tablespoon tomato paste
12 ounces hot Italian sausage (if links, remove casings)
12 ounces sweet Italian sausage (if links, remove casings)
8 slices provolone
1/4 cup mayonnaise
3 tablespoons pesto
4 ciabatta rolls, buttered and lightly toasted
Pickled banana peppers, for topping