Slightly pound the beef steaks and make cuts with a knife around the edges. Salt and pepper the steaks from both sides.
Dip one side of each steak in flour.
Heat cast iron or stainless steel pan, add oil. Place the steaks with the floured side into the oil, turn and sear on both sides. The meat should remain slightly pink inside. Remove the meat from the pan and keep warm on a preheated plate (e.g., in the oven).
In the drippings, foam the butter, sprinkle with a teaspoon of flour, pour in the beef broth, and stir well. Season the gravy to taste with salt and pepper. Add the meat and let it stew briefly until soft.
Meantime, dust the sliced onions with flour and roast them in the hot fat until brown. Immediately strain, drain, and lightly salt.
Cover the beef steaks with crispy onions and pour the gravy over them.