Bring all the marinade ingredients to the boil in a small saucepan. Take off the heat and allow to cool completely. Marinade the tuna in this sauce for at least 20 minutes. Pat dry the tuna and drizzle lightly with olive oil before grilling. Now reduce the marinade by halve until the syrup is thick. Strain through a fine sieve. When the tuna has cooked, slice up quickly whilst still warm. Carefully remove the leaves of the lettuce. You will be using the leaves as wraps to roll up the ingredients in. Lay the lettuce leaves out on a large chopping board and top up with the cucumber strips, onions, grapefruit segments and some fresh herbs herbs. Top up with slices of tuna and finally drizzle over the prepared sauce and sprinkle the sesame mixture on top. Fold the lettuce leaf around the filling to obtain a fresh lettuce wrap. Serve immediately.

MANUEL