Pre-heat the oven to 200°c. Put the peppers, onion, tomatoes and olives into a large, deep baking tray and cook for 15 minutes until they start to soften and char at the edges.
Stir in the passata and butter beans and season with salt and pepper, to taste.
Lay the cod loins on top and return to the oven for a further 15 minutes, until the cod is cooked through.
Sprinkle over the basil and serve with steamed rice.