Set the oven to 200C/180C fan/gas mark 6.

Place 1tbsp olive oil in a frying pan over a low-to-medium heat.

Add the onion and cook gently without colouring for 3-4 minutes, stirring constantly, then add the garlic and cook for a further minute. Remove from the heat.

Add the onion, garlic, olives and tomatoes to a bowl, season and mix well.

Transfer the tomato sauce to a casserole dish and place the cod on top. Drizzle 2tbsp olive oil over the fish.

Place the casserole dish in the oven for 15-20 minutes or until the cod is just cooked.

Sprinkle the basil over the cod and serve on warmed serving plates.