Bring salted water to a boil in a large pot. Add uncooked pasta and cook according to package directions until al dente, about 8-10 minutes. Drain and reserve a cup of pasta water.

Heat olive oil in a large skillet over medium-high heat. Sauté chopped onion for 4-5 minutes until translucent and fragrant.

Add ground beef and minced garlic to skillet. Brown the beef for about 8 minutes, breaking it up until no pink remains. Drain excess fat if needed.

Stir in diced tomatoes, tomato paste, Dijon mustard, and Italian seasoning. Allow to simmer for 4-5 minutes until slightly thickened.

Reduce heat to medium and mix in heavy cream, cooking for another 3-5 minutes until heated through.

Season sauce with salt and black pepper. Fold in drained pasta, adding reserved pasta water if necessary to adjust consistency.

Remove from heat and top with grated Parmesan cheese if desired. Serve hot.