• Roast spaghetti squash according to directions. While the squash roasts, make your sauce.
• Add oil to a large sauté pan over medium heat. Add sausage and cook until brown, using a wooden spatula to break it into bite-sized chunks. Add diced yellow onion and cook for 4-5 minutes, or until the onion has softened in texture and color. Add the red onion and peppers, reduce heat to low, and cook for about 12 minutes, or until the peppers have softened. Add garlic and crushed red pepper and cook for 2 minutes, then add whole peeled tomatoes (add them with your hands, lightly crushing them as you place them in the pot), their juices, Italian seasoning, and salt. Increase heat to medium-high and bring the sauce to a boil. Once it reaches it a rolling boil reduce the heat to a simmer and cook on low for 45 minutes. When ready to use, taste the sauce and adjust the seasoning as needed.

Assembly:

• Preheat oven to 400 degrees (F). Line a large baking sheet with aluminum foil; set aside.
• In a large bowl combine the scooped out spaghetti squash flesh with 2 1/4 cups of the sausage sauce and 3 tablespoons of the parmesan cheese, mix well to combine.
• Divide the saucy spaghetti squash mixture among the four empty squash shells, top with mozzarella and remaining parmesan, and place on prepared pan. Bake for 8-10 minutes, or until cheese has completely melted. Serve at once!