Cook the pasta. Bring a large pot of salted water to a boil and cook the spaghetti according to the package directions until al dente. Drain well and set aside.

Prepare the seasoned coating. Add the flour, salt, black pepper, garlic powder, and Italian seasoning to a large zip-top bag. Seal the bag and shake until the seasonings are evenly combined.

Coat the chicken. Place the chicken cutlets in the bag with the seasoned flour. Seal and shake gently until each piece is evenly coated, then shake off any excess flour.

Cook the chicken. Heat the oil in a large skillet over medium-high heat. Add the chicken and cook until golden brown on both sides and the center reaches 165°F.

Set the chicken aside. Transfer the cooked chicken to a clean plate and reduce the skillet heat to medium.

Start the sauce. Add the butter to the same skillet and allow it to melt. Stir in the chopped onion and cook until tender and translucent.

Add the aromatics. Stir in the diced tomatoes and minced garlic. Cook for about 30 seconds, just until the garlic becomes fragrant.

Thicken the base. Sprinkle the flour over the vegetables and stir continuously until no dry flour remains.

Season the sauce. Add the Italian seasoning and red pepper flakes, stirring them into the skillet.

Make it creamy. Slowly whisk in the heavy whipping cream, then add the Parmesan cheese and salt. Cook over medium to medium-low heat, stirring regularly, until the cheese melts and the sauce becomes creamy and slightly thickened.

Combine with the pasta. Add the drained spaghetti to the skillet and toss until all of the noodles are evenly coated in the Parmesan cream sauce.

Finish and serve. Return the chicken to the skillet, spooning some of the creamy sauce over the top. Warm everything together briefly, then serve immediately.