1.To make tapenade, process olives, anchovies and capers until finely chopped but not a smooth paste. Transfer to a bowl and stir in garlic, oil, thyme, mustard, rind and 1 tablespoon of orange juice.
2.Place tuna steaks in a shallow baking dish and spread each one with a generous tablespoon of tapenade. Pour around remaining orange juice and wine, and cook under a preheated grill for 5 minutes, until fish is opaque but still slightly translucent in centre.
3.Serve tuna steaks with steamed baby potatoes, baby rocket and lemon wedges. Season and pour over pan juices, if you like.
This makes 1 1/2 cups tapenade. Serve with pasta or on sandwiches.