Rub the fish with pepper and the olive oil, then sprinkle with lemon juice and leave to marinate while you prepare the tomatoes. Combine the tomatoes, olive oil, garlic and half the herbs in a bowl and season with salt and pepper.
Preheat the grill to its highest temperature. Grill the tuna for only about 4 minutes each side, then season with salt. Try to get the outside of the steaks b