This is a recipe you can experiment with to determine your personal taste. Simply rub the sashimi grade tuna with olive oil, then dredge in coarsely-ground black pepper and kosher salt.

Heat a large heavy dry skillet over high heat until very hot and smoking, for about 4 minutes. Add the tuna and sear for 3 minutes on one side, 3 minutes on the opposite side, the 2 minutes each on the remaining sides. Remove the tuna from the skillet and cool to room temperature. Then, thinly slice the tuna and sprinkle it with soy sauce. I usually serve the tuna with wasabi mayonnaise (you can buy this or make it yourself by combining good-quality mayonnaise with wasabi paste to taste.)