Preheat the oven to Gas Mark 4, 180°C (350°F).
In a small bowl combine the paprika, lemon zest, a little salt and 2 tablespoon of oil. Brush this mixture all over the pork and allow to sit for a couple of minutes while you prepare the tomato mixture.
Heat a little oil in a large frying pan over a medium heat. Add the onion and garlic and cook for a couple of minutes. Then add the chilli, bay leaf, rosemary leaves, tomatoes, water, beans and sugar. Season with a little salt and black pepper. Stir well. Bring up to gentle simmer. Transfer to an ovenproof dish and place the pork fillets on top.
Place in the preheated oven. Cook for 40 minutes. Add a little extra water if the bean and tomato mixture is drying out.
Remove the pork to a board and allow to rest for 5 minutes. Stir the lemon juice and parsley through the bean and tomato mixture. Discard the bay leaf. Taste and season with a little more salt and pepper if necessary.
Carve the pork into thin slices and serve with the bean and tomato mixture, some crusty bread and a green salad.