Preheat your oven to 150°C (fan-forced).
In a large oven-safe pot or Dutch oven, heat a drizzle of olive oil over medium heat. Add the pork pieces and cook until browned, then remove and place on a plate.
Add the leek, fennel, celery and garlic, and sauté for 5–7 minutes until soft and fragrant.
Stir in the tomato paste and cook for 1 minute to caramelise slightly. Add the apple cider vinegar to deglaze the pan, scraping up any bits from the bottom.
Return the pork pieces to the pot. Add the bone broth, thyme, bay leaves and lemon zest. Season with a little salt and pepper if desired.
Cover with a lid and transfer to the oven. Cook for 2.5 hours, then remove the lid and stir in the cannellini beans.
Return to the oven for another 30 minutes, uncovered, until the pork is tender and the broth has thickened slightly.
Once out of the oven, stir through the lemon juice to brighten the flavour. Taste and adjust seasoning as needed.