Fill a large pot with water and bring to a boil. Add salt and penne pasta; cook until al dente, about 8-10 minutes. Reserve 1 cup of pasta water, then drain pasta.

Heat olive oil in a large skillet over medium heat. Sauté diced onion for 3-4 minutes, then add minced garlic and cook for an additional minute.

Add ground beef, breaking it apart with a spoon. Cook until browned, about 6-7 minutes. Season with salt, pepper, and Italian seasoning.

Reduce heat to medium-low. Stir in heavy cream and reserved pasta water; simmer until sauce thickens slightly. Add Parmesan cheese and stir until melted.

Fold in cooked penne pasta, ensuring it is well coated. Adjust sauce consistency with more pasta water if necessary.

Plate the creamy beef pasta, garnishing with extra Parmesan or parsley if desired. Serve hot.