Form beef into three 5 to 6 ounce hamburger patties. Use your thumb to imprint a dimple into the middle of each burger. (This prevents the middle of the burgers from puffing up while cooking). Season both sides of the hamburgers with salt and pepper.
Melt 1 tablespoon of butter in a cast iron pan over medium heat. Cook hamburger patties 3 to 4 minutes on each side, depending on how well done you like it.
Rest burgers covered loosely with aluminum foil for 5 minutes then serve on a buttered bun with lettuce, tomatoes and onion (or how you like it).