Season the steak generously on both sides with seasoning salt, patting the seasoning into the meat.
Heat a heavy skillet, preferably cast iron, over medium heat until hot. Add the oil. When oil is hot, add the steak and cook until seared and well-crusted on one side, about 4 minutes. Turn and cook 3 minutes more for medium-rare and 4 minutes for medium.
Transfer to a cutting board and let rest, loosely covered with foil, while you prepare the salad.
Divide the lettuce between two plates. Slice steak, trimming away fat. Arrange sliced steak on top of lettuce on both plates. Sprinkle with a mixture of the herbs, adorn with chopped tomato, and drizzle with vinaigrette.