Heat up the oil in a frying pan. Add the pancetta to sweat in the pan. Add the onions, celery and parsley stems and fry until tender. Add the white wine and boil down, then add the tomatoes and olives and allow to simmer until the tomatoes collapse.
Add the fish and keep simmering until the fish is ready. Add the parsley and rice. Add salt, pepper and lemon juice to taste, and place on one side.
Preheat the oven to 180 ºC (360 ºF). Cut the tops off the bell peppers remove the seeds and white pith. Fill them with the fish mixture. Put the tops back on and place them in an ovenproof dish. Pour some olive oil over the top and bake in the oven until the peppers are cooked and black spots start to appear on the skin.
Serve the dish and have a lovely meal!