Buy sliced liver 1/4 to 1/2 inch thick. If too thin, it over cooks quickly.
Melt a small amount of butter in a skillet on medium-low heat.
Flour the liver if you wish. This adds a crust that some people enjoy. Add salt and pepper.
Add liver slices to hot fat. Fry on one side for about 3 to 4 minutes. Do not cover the pan. Turn and fry on the other side, then cover the pan. The total cooking time should be about 8-10 minutes, depending on thickness of the liver.
To test for doneness, cut in the thick part with a knife. If red juices flow or the meat is pink continue cooking a short time longer.
Liver is one of nature's nutrition bargains. It is an excellent source of protein, iron, vitamin A & B. Beef liver is relatively low in cost, free of fat and bone. It's easy to prepare in a short time.