This beef casserole is a quick and easy budget-friendly meal, made with tender cube steak, potatoes, and carrots. Cube steak is a thin piece of steak that has been tenderized, usually by a machine or with a mallet. If you can't find cube steaks, you can tenderize sirloin or top round steaks yourself. Cover the steak with a sheet of plastic wrap and pound it with the coarse side of a meat mallet until the steak has a cross-hatched, or cubed, appearance. Alternatively, use a sharp knife to make the cross-hatching over the top of the meat without cutting through.