Bring a large pot of salted water to a boil, using at least 1 tablespoon of salt. Cook the pasta 1–2 minutes less than the package instructions. Reserve 1 cup of the boiling pasta water, then drain and set the pasta aside.

Heat the olive oil in a large pan or Dutch oven over medium heat. Add the diced onion and cook for about 5 minutes, stirring occasionally, until soft and translucent.

Add the ground turkey and cook over medium to medium-high heat, breaking it into small pieces, until fully cooked through.

Season the turkey with half of the salt, black pepper, and Italian seasoning. Stir in the minced garlic and cook for about 1 minute, until fragrant.

Sprinkle the flour over the turkey mixture and stir well to combine. Pour in the chicken broth and tomato sauce and bring the mixture to a gentle simmer.

Add the cooked pasta to the pan and pour in the half-and-half. Stir until the pasta is evenly coated and the sauce begins to thicken.

For a thinner sauce, gradually add additional chicken broth or reserved pasta water. For a creamier sauce, add additional half-and-half as needed.

Season with the remaining salt and additional black pepper to taste. Stir in half of the mozzarella cheese and half of the cheddar cheese.

Sprinkle the remaining mozzarella and cheddar over the top. Reduce the heat to low and cover the pan or Dutch oven with a tight-fitting lid until the cheese is fully melted.

Remove from heat and garnish with fresh parsley and red chili flakes if desired. Serve warm.