Bring a large pot of salted water to a rolling boil. Cook the penne pasta until al dente, about 10-12 minutes. Reserve 1 cup of pasta water, then drain and set aside.

Heat olive oil in a skillet over medium heat. Sauté the diced onion and garlic for about 5 minutes until the onion is translucent.

Add the ground beef to the skillet, breaking it apart. Cook for about 7 minutes until browned. Season with salt, pepper, and Italian seasoning.

Lower heat and stir in the heavy cream. Gradually add reserved pasta water until the sauce reaches desired consistency. Fold in Parmesan cheese until melted.

Toss the cooked pasta in the sauce until thoroughly coated. Cook together for 1 minute, then serve hot with extra Parmesan or parsley.