Preheat your oven to 240ºC/475ºF/gas 9. First, score the skin of the pork in a criss-cross pattern every 1cm/½ inch with a sharp knife, trying not to cut into the meat itself. Mix a little salt with a teaspoon of paprika, the lemon juice and a little olive oil, then rub this over the meat and into the score lines. Put the meat in a high-sided roasting tray and cook in the preheated oven for 30 minutes to start the skin crisping up.
Remove the meat from the oven, turning the heat down to 180ºC/350ºF/gas 4. Take the pork out of the tray and put it to one side, then spoon out half the fat and discard it. Place the tray on the hob, add the onions, whole chillies, chorizo, bay leaves and rosemary with the remaining paprika, and fry gently until the onions are soft. Add all the tomatoes, the beans, garlic, parsley and a wineglass of water to the tray, stirring and scraping up all the lovely sticky bits from the bottom. Place the pork on top, return to the oven and cook for another hour or so or until the skin is crispy and the meat is meltingly tender.
When cooked, remove the pork from the tray and allow to rest. Taste the sauce and season with salt, pepper and a few swigs of red wine vinegar to give it a twang. Then remove the chillies and control the heat by chopping up as much chilli as you like and stirring it back into the sauce. Lovely served with soured cream.