Marinate the salmon in the olive oil and lemon juice for 2 - 3 hours.
Wash the lettuce leaves and place on a large round plate.
Remove the salmon from the marinade and cut into thin strips (about 2cms) place on a baking tray with a knob of butter spread on it to prevent sticking.
Place the baking tray under the grill for a few seconds turning the salmon once so that itīs done on both sides.
Place the strips of salmon on top of the lettuce leaves and pour some of the marinade onto it adding a few drops of white wine vinegar.