Bring a large pot of salted water to a boil. Cook the penne according to package directions until al dente. Reserve 1 cup of the pasta water. Drain the pasta and set aside.

Heat a large skillet over medium heat. Add the olive oil. When it shimmers, add the diced onion and minced garlic. Sauté for about 5 minutes until the onion is soft and fragrant.

Increase the heat slightly and add the ground beef. Break it apart with a spatula. Brown the beef for about 7 minutes until no pink remains. Season with salt, pepper, and Italian seasoning while it cooks.

Lower the heat to medium-low. Pour in the heavy cream and stir to combine. Add reserved pasta water a little at a time until the sauce reaches your desired consistency. Start with 1/4 cup and add more as needed.

Stir in the grated Parmesan. Keep stirring until the cheese is melted and the sauce is smooth. Taste and adjust salt and pepper.

Add the cooked penne to the skillet. Toss gently to coat every piece with the sauce. Warm through for a minute so the flavors meld.

Serve hot, topped with extra Parmesan or chopped fresh parsley if you like.