Pat steaks dry and cut 3 slits (1 inch long and 1/4 inch deep) 1 inch apart across center cartilage of each steak (to keep from curling), then sprinkle with 1/2 teaspoon salt and 1/4 teaspoon pepper.
Heat 1 tablespoon oil in a 12-inch heavy skillet over moderately high heat until hot but not smoking, then cook steaks, turning over once, until meat is just medium-rare, 4 to 7 minutes total.
While steaks cook, pulse herbs with zest, lemon juice, garlic, and remaining 1/4 cup oil, 1/4 teaspoon salt, and 1/4 teaspoon pepper in a food processor until finely chopped.
Transfer steaks to a platter and let stand, loosely covered with foil, 5 minutes, then serve with sauce.
