Heat a little olive oil in a large pan over medium heat. Add the onion and cook until soft about 4 mins.
Add garlic for 1 min.
Add ground beef and break it up with a spoon. Season with 1 tsp of your salt and cook until well browned.
Stir in the tomato paste and cook for 1-2 minutes.
Add tomatoes and break them up with a wooden spoon.
Reduce heat to low. Stir in heavy cream and 2 more tsp. of salt.
Add parmesan rind and simmer gently, stirring occasionally 15-30 mins uncovered.
Toward the end of cooking, sprinkle the 1/2 cup grated Parmesan over the sauce and stir in.
Remove rind and toss sauce with buttered and salted pasta.
If you have leftovers, add a bit of the pasta water to the container so it isn't dry the next day!
Add more salt when serving to taste if needed. (We like a lot of salt!) and serve with more parmesan cheese!