Cook rigatoni according to package directions until al dente. Drain and set aside, reserving 1/2 cup of pasta water.

In a large skillet over medium-high heat, cook the ground beef, breaking it into crumbles, until fully browned. Drain excess fat.

Add the diced onion to the skillet and cook for 3-4 minutes until softened. Stir in the garlic and tomato paste, cooking for another minute until fragrant.

Pour in the beef broth, ketchup, and mustard. Stir to combine and simmer for 2-3 minutes.

Reduce heat to low. Stir in the heavy cream, then add the shredded cheddar a handful at a time, stirring until each addition is fully melted and smooth.

Add the cooked rigatoni to the sauce and toss until every piece is coated. Add a splash of reserved pasta water if needed to loosen the sauce.

Serve immediately, topped with fresh chopped parsley.