01 - Bring a pot of salted water to a rolling boil over high heat. Add the pasta and cook according to package directions until al dente. Reserve 1/2 cup of the pasta cooking water before draining the pasta. Set aside.
02 - In a large skillet, heat the olive oil over medium-high heat. Add the ground turkey, breaking it apart with a spoon to ensure even cooking. Cook until the turkey is thoroughly browned. Season with salt, black pepper, and Italian seasoning. Remove the browned turkey from the skillet and set aside.
03 - In the same skillet used for the turkey, add the finely chopped onion. Cook over medium heat for 2-3 minutes, or until the onion has softened. Add the minced garlic and cook for an additional 30 seconds until fragrant.
04 - Pour the marinara sauce and broth into the skillet with the sautéed aromatics. Stir well to combine. Bring the mixture to a gentle simmer. Stir in the heavy cream and optional red pepper flakes. Allow the sauce to simmer for 5 minutes, allowing the flavors to meld.
05 - Add the cooked ground turkey back into the skillet. Reduce the heat to low. Gradually stir in the shredded cheddar cheese until it is completely melted and the sauce is smooth and creamy. Stir in the grated Parmesan cheese until well combined.
06 - Add the drained, cooked pasta to the skillet with the cheese sauce. Toss gently to ensure all the pasta is evenly coated. If the sauce appears too thick, add a small amount of the reserved pasta water, a tablespoon at a time, until the desired consistency is reached.
07 - Remove the skillet from the heat. Garnish the dish generously with fresh chopped parsley or basil. Serve immediately with additional grated Parmesan cheese, if desired.