To make the salsa, place tomatoes in a bowl with the capers, olives, parsley and chilli. Combine lemon juice and olive oil, season with salt and pepper, then set aside 2 tablespoons and add the rest to the salsa mixture. Toss to combine.

Heat a chargrill or non-stick frypan over high heat. Brush tuna with a little oil and, when the grill is hot, sear for 1-2 minutes on each side. (Make sure it's still rare in the middle as it will continue to cook once removed from the heat.)

Cut each tuna steak into 3-4 pieces. Toss salad leaves with remaining dressing and pile onto 4 plates. Add tuna pieces and divide the salsa between each plate. Serve with lemon wedges if desired.