Preheat grill or sauté pan (cast iron works best) as hot as you can get it.
Brush tuna steaks with olive oil. Season with salt and pepper and place on hot grill or pan.
For very rare seared steak (cold in center) about 30 seconds on each side.
For rare to medium rare seared steak 90 seconds (warm in the center) on each side.
For pink in the center reduce heat and continue grilling for 1 minute on each side.