Brush the tuna steaks with olive oil, then season with salt and pepper. Sprinkle with sesame seeds if using and press them lightly into the tuna.
Heat a skillet, cast iron pan or grill pan over medium-high heat. Once hot, cook the tuna for 2 minutes on one side, then flip and cook for another 2 minutes for rare. If you’d like it cooked more, cook for 3 minutes on each side. It should still be a little pink inside to avoid overcooking.
Remove from the pan and allow to rest for 5 minutes. Serve whole or sliced against the grain in 1-inch thick slices.
If grilling, cook over medium heat and cook for the same amount of time as above for your preferred level of doneness.
