Bring a large pot of salted water to a boil over high heat. Add penne pasta and cook according to package instructions until al dente, typically 8–10 minutes. Reserve 1 cup of pasta water, drain, and set aside.

In a large skillet, heat olive oil over medium heat. Add diced yellow onion and sauté for 3–4 minutes until translucent. Stir in minced garlic and cook for an additional minute.

Increase heat to medium-high and add ground beef. Brown evenly for about 7 minutes. Season with salt, pepper, and Italian seasoning.

Lower the heat to medium, add heavy cream and stir. Gradually add reserved pasta water until desired consistency is reached. Stir in Parmesan cheese until melted.

Add drained penne pasta to the skillet and toss gently for 2 minutes to coat in the sauce.

Serve immediately, garnishing with additional grated Parmesan cheese and parsley if desired.