In a medium bowl combine chopped tomatoes and olives. Chop hard boiled egg and add to bowl. Add parsley. Drizzle with lemon juice and olive oil. Sprinkle with salt and pepper; toss to combine.
Heat a pan over medium-high to high heat on the stove.
Rub the tuna steaks all over with olive oil; sprinkle both sides with salt and pepper. Place the tuna in the pan and don’t touch it. Let is sear on one side for about 2-3 minutes (depending on the thickness) or until nice and brown. Turn over and let sear for another 2 minutes on the other side.
Put the tuna on each plate and spoon the Niçoise relish over the top.