Cook the pasta: Bring a large pot of salted water to a boil. Add the spaghetti and cook according to the package instructions until al dente. Reserve 1 cup of pasta water, then drain the pasta and set aside.

1. Cook the turkey: In a large skillet, heat olive oil over medium heat. Add ground turkey and cook, breaking it apart with a spoon. Cook for 5-7 minutes until browned and cooked through. Season with salt, pepper, oregano, basil, and red pepper flakes (if using).
2. Sauté the onions and garlic: Add diced onion to the skillet and cook for 3 minutes until softened. Add minced garlic and cook for another 30 seconds until fragrant.
3. Make the sauce: Stir in crushed tomatoes and tomato paste, mixing well. Let the sauce simmer for 10-15 minutes, allowing the flavors to meld. Adjust seasoning with more salt, pepper, or herbs as desired.
4. Combine the pasta and sauce: Add the cooked spaghetti to the skillet and toss to coat in the sauce. If the sauce is too thick, add a little of the reserved pasta water to reach the desired consistency.
5. Serve: Garnish with fresh parsley and Parmesan cheese if desired. Serve immediately.