1. Rinse beef steak and pat dry. Pat salt, pepper, onion flakes, and garlic flakes evenly onto meat.
2. Pour olive oil into an 8- to 10-inch ovenproof nonstick frying pan over high heat; tilt to coat pan bottom. When hot, add steak and brown on both sides, about 4 minutes total. Supporting meat with tongs, tip steak onto its edge and rotate to brown lightly, about 2 minutes total. As fat in pan accumulates, wipe out with paper towels.
3. Put pan with steak in a 400° regular or convection oven and bake until meat is done to your taste (cut to test), 8 to 12 minutes for rare or about 25 minutes for well done.
4. Turn oven heat to broil. Remove pan and wipe out fat with a paper towel. Mound French onions onto meat and sprinkle with cheese. Broil in pan about 6 inches from heat until cheese is bubbling and beginning to brown, 3 to 4 minutes. Remove pan from oven and pour broth around meat, stirring to release browned bits.
5. Leave meat in pan or use a wide spatula to transfer steak and onions to a warm rimmed platter (pour juices around meat). To serve, cut meat and onions into 4 equal portions; set each on a rimmed plate and spoon juices around meat.