Choose a heavy skillet that is large enough to hold the number of tuna steaks you are cooking. Add 1 tablespoon of oil and 1 tablespoon of butter in a skillet. Melt the butter in a skillet over medium-high heat.
Place the tuna steaks on top. When the steaks are added, they should sizzle. Cook, uncovered for about 4 to 6 minutes per 12-inch thickness, or until fish begins to flake when checked with a fork but remains pink in the center, turning once during cooking. Adjust the heat as required if the skillet gets too hot.