- 1 tablespoon olive oil
- 2 pounds sweet Italian sausage
- 1 pound fresh mushrooms, sliced
- 1 onion, chopped
- 1 green bell pepper, chopped
- 1 tablespoon minced garlic
- 2 (28 ounce) cans tomato sauce
- 2 tomatoes, diced
- 1 (6 ounce) can tomato paste
- 1 (6 ounce) can sliced black olives, drained
- 1 teaspoon dried oregano, or to taste
- 1 teaspoon dried basil, or to taste
- salt to taste
- 1 (16 ounce) package spaghetti, or as needed
- 1/4 cup grated Parmesan cheese, or to taste
- Heat olive oil in a large skillet over medium-high heat. Cook and stir sausage, mushrooms, onion, green bell pepper, and garlic in the hot oil until sausage is browned and crumbly, about 20 minutes; drain and discard grease.
- Stir tomato sauce, diced tomatoes, tomato paste, and olives into sausage mixture; season with oregano, basil, and salt. Simmer mixture until flavors infuse, about 30 minutes.
- Bring a large pot of lightly salted water to a boil. Cook spaghetti in the boiling water, stirring occasionally until cooked through but firm to the bite, about 12 minutes. Drain and transfer to a serving bowl; top with tomato-sausage sauce and Parmesan cheese.