Bring a large pot of salted water to a boil. Add the spaghetti and cook according to package instructions until al dente. Drain well and set aside.
While the pasta cooks, heat a large skillet over medium-high heat. Add the ground beef and cook, breaking it apart, until browned and no longer pink. Drain excess fat if necessary. Add the chopped onion, minced garlic, and chopped bell pepper to the skillet. Sauté for about 5 minutes until vegetables are softened and fragrant.
Stir in the marinara sauce and drained diced tomatoes. Sprinkle in the dried oregano, dried basil, salt, and black pepper. Reduce heat to low and simmer the sauce for 10 minutes, stirring occasionally to meld the flavors.
In a medium bowl, combine the cottage cheese, 1 cup of the shredded mozzarella, and the grated Parmesan. Stir until smooth and evenly mixed.
Preheat your oven to 375°F (190°C). In your baking dish, spread half of the cooked spaghetti evenly. Spoon half of the meat sauce on top, then dollop half of the cheese mixture over the sauce. Repeat layering with the remaining spaghetti, meat sauce, and cheese mixture. Finally, sprinkle the remaining 1 cup of mozzarella cheese evenly over the top.
Place the casserole in the preheated oven and bake for 25-30 minutes, or until the cheese is bubbly and golden brown on top.
If using, sprinkle crumbled turkey bacon over the casserole as soon as it comes out of the oven for an added smoky crunch. Finish with a generous sprinkle of fresh parsley. Let the casserole rest for 5 minutes before serving to allow it to set.