Bring a large pot of salted water to a boil. Cook pasta until al dente. Reserve ½ cup pasta water, then drain.
Heat a large skillet over medium-high heat. Add ground beef and cook until browned, breaking it apart as it cooks. Drain excess fat if needed.
Add diced onion and cook until softened, about 3–4 minutes. Stir in garlic and cook until fragrant.
Reduce heat to medium. Pour in heavy cream and stir to combine. Let simmer gently for 3–4 minutes.
Lower heat and stir in Parmesan cheese until melted and smooth.
Add cooked pasta and toss to coat evenly. Add reserved pasta water a little at a time to loosen the sauce if needed.
Season with salt, black pepper, and Italian seasoning. Taste and adjust seasoning.
Serve hot with extra Parmesan if desired.