Blanch the leek in boiling salted water for 1 minute and drain. Cut the fish into cubes, season with salt, pepper and dust with flour. Fry the fish in a pan with 3 tablespoons of olive oil, remove and keep warm.
Put the rest of the olive oil in the pan and briefly sweat the pineapple in it. Stir in the soy sauce and add the leek. Wash the tomatoes, cut them into small pieces and add to the pineapple.
Simmer briefly and season with salt, pepper and chili powder. Add the fish cubes again and let them steep for 5 minutes over a low heat. Serve with rice.