Heat the oil in a saucepan over a low heat and gently fry the onion for 5 minutes until soft and golden. Add the carrot, celery and garlic and fry gently for another 5 minutes.
Stir in the pork, rosemary and lemon rind, and fry for a few minutes until the pork is lightly browned all over. Season with salt and pepper.
Add the tomatoes and stock. Bring to the boil, then gently simmer over a low heat for 30 minutes. Serve hot with rigatoni or penne pasta, drizzled with a little extra olive oil and garnished with the rosemary, if liked. Serve the grated Parmesan in a bowl at the table for sprinkling over the top.