Soak fish overnight, changing the water several times, or boil it for 30 minutes to an hour in order to reduce the saltiness of the fish. You may take a taste test afterward to make sure the fish is not too salty.
Rinse the fish and flake it into small bites.
Put oil in a frying pan, heat and add onions, thyme, garlic and the scotch bonnet pepper slices (Note: Scotch bonnet peppers are very spicy so you may need to adjust the amount. Also, green scotch bonnets are milder than the red ones). Stir for 2 minutes.
Add fish and stir for 2 minutes.
Drain ackee, stir into pan taking care not to crush it or break it apart too much.
Stir in tomatoes and cook a little longer till they are soft.
Take a taste test. Sprinkle with pepper and add salt if needed.