Cook the spaghetti according to package instructions until al dente. Drain and set aside.
In a large skillet, heat olive oil over medium heat. Add the diced onion, bell pepper, and minced garlic. Sauté until soft, about 5 minutes.
Add the ground turkey or beef to the skillet. Cook until browned and fully cooked through, breaking it into small pieces as it cooks.
Stir in the diced tomatoes, tomato sauce, Italian seasoning, cayenne pepper, salt, and black pepper. Mix well and let simmer for 5-7 minutes.
In a large bowl, combine the cooked spaghetti, cream cheese, and sour cream. Mix until the spaghetti is well coated and creamy.
In a large baking dish, layer half of the spaghetti mixture on the bottom. Pour half of the meat sauce over it, then top with half of the shredded cheddar cheese. Repeat the layers with the remaining spaghetti, meat sauce, and cheddar.
Cover the baking dish with aluminum foil and bake in the preheated oven for 25 minutes. Then, remove the foil and bake for an additional 10-15 minutes until the cheese is bubbly and golden.
Once baked, remove from the oven and let it cool for a few minutes. Garnish with chopped parsley before serving.