To make the salsa, heat the olive oil in a large frying pan, add the onion and fry over a medium heat until softened but not coloured. Add the chilli and garlic and fry for another minute. Stir in the tomatoes and olives and warm through for 1 minute. Remove from the heat, stir in the basil and season.
Dust the cod fillets in the flour and shake off the excess. Heat the olive oil in a large frying pan, add the fillets, skin-side down, and fry for 3-4 minutes, turn over and fry for another 2-3 minutes or until the cod is opaque and the skin is golden and crisp.
To serve, divide the cod fillets between 4 plates, top with the tomato salsa and serve with steamed green beans or Tenderstem broccoli.