Portion the tuna into 3-4 steaks (1 to 1½ inches thick).
Generously rub salt and freshly cracked black pepper onto each side of the steaks. Let sit in the refrigerator for 20 minutes.
When ready to cook, heat a skillet large enough to hold the steaks over high heat. Add just enough oil to coat the pan and add the steaks. Cook each side for no more than a minute (it should be rare in the middle).
Slice and serve on steamed rice with soy sauce. A topping of spicy mayonnaise is a welcome garnish.