1 tablespoon olive oil
1 pound mild or hot Italian sausage
1 onion, chopped
2 red bell peppers, cut into 1-inch pieces
1 3/4 teaspoons salt
3 cloves garlic, minced
1 cup canned crushed tomatoes in thick puree
1 cup canned low-sodium chicken broth or homemade stock
2 tablespoons dry vermouth or dry white wine
3 tablespoons chopped flat-leaf parsley
3/4 pound whole-wheat spaghetti
2 tablespoons grated Parmesan cheese, plus more for serving