Beef on weck is a Western New York sandwich: thin-sliced rare roast beef piled on a kummelweck roll, a kaiser-style roll topped with coarse salt and caraway seed, served with horseradish and the beef's own jus. The name is a shortening of kummelweck. It is regional enough that you will meet it constantly at Buffalo-area events and rarely at fairs downstate.
Also known as: weck.