Warm the oil in a frying pan over a medium heat. Add the onion and garlic and cook and stir for several minutes until soft. Add the lemon juice, chilli, bay leaves and coriander and give a good stir.
Add the fish to the pan and cook gently, turning occasionally. After about 5 minutes, add the tomatoes and allow to simmer for 10 minutes or until the fish is evenly white throughout and the flesh flakes easily with a fork. Serve with accompanying veg/rice or bread and butter!