1. Bring a large pot of salted water to a boil and cook the penne until al dente. Reserve 1 cup of pasta water, then drain the pasta and set aside.

2. In a large skillet over medium-high heat, cook the ground beef until browned, breaking it into crumbles as it cooks. Drain excess grease if needed.

3. Reduce the heat to medium and add 2 tablespoons of butter and the chopped onion. Cook for 2 to 3 minutes until softened.

4. Stir in the minced garlic and cook for 30 seconds until fragrant.

5. Add the remaining 2 tablespoons of butter and pour in the beef broth.

6. Season with Italian seasoning, salt, black pepper, and red pepper flakes if using. Simmer for 2 to 3 minutes.

7. Add the cooked pasta to the skillet and toss well to coat in the garlic butter beef mixture.

8. Stir in the Parmesan cheese and add a splash of reserved pasta water if needed to loosen the sauce.

9. Finish with chopped parsley and serve hot with extra Parmesan on top.