Preheat oven at 180° C.

• Clean and salt fish. Refrigerate for several hours.
• Chop onions

1.  Allow fish to return to room temperature, sprinkle with olive oil and bake in moderate oven until flesh seems to flake apart easily under a fork.

2.  Meanwhile fry onions in olive oil until yellow.

3.  Beat lemon juice and water slowly into the tahini, adding more lemon juice to taste if necessary. The tahini sauce will become very creamy.

4.  Mix onions into sauce, pour over the baked fish and return it to the oven.

5.  Bake about 20 minutes in moderate oven. Some of the sauce will be absorbed into the fish and the onions will be very well cooked.

6. Serve this dish cold.