Spread onions, garlic, bell peppers and black olives on the bottom of a baking pan and bake in the oven at 220°C for about 15 minutes or until soft and lightly burned on the edges. Remove from the oven.
Stir in chopped tomatoes, tomato puree and cannellini beans, seasoned with sea salt and pepper.
Place cod fillets on top, season with remaining salt and pepper, and sprinkle with olive oil. Bake in the oven for another 15 minutes until the fish fillets are done.
Sprinkle with chopped parsley and serve with polenta.