Recipe: Italian Sausage and Peppers Baked Ziti

Name: Recipe: Italian Sausage and Peppers Baked Ziti
Ingredients: 1 tablespoon olive oil; 1 pound uncooked Italian sausages, casings removed; 2 medium bell peppers, diced; 1 medium yellow onion, diced; 2 teaspoon garlic, finely chopped; 1/2 teaspoon red pepper flakes (optional); 4 cups marinara sauce (about 36 ounces); 1/2 teaspoon kosher salt, plus more for seasoning; Freshly ground black pepper; 1 pound dried ziti or penne pasta; 1 cup whole-milk ricotta cheese; 1/2 cup finely grated Parmesan cheese, divided; 1/4 teaspoon kosher salt; 8 ounces shredded mozzarella and/or provolone cheese (about 2 cups)