Alan Geisler

Alan Stark Geisler (September 30, 1930 – January 6, 2009) was an American food chemist, best known for creating the red onion sauce most often used as a condiment topping on hot dogs in New York City. Specifically, the sauce, which is marketed as Sabrett's Prepared Onions, is usually served on Sabrett brand hot dogs sold by New York's many pushcart hot dog vendors.

Sabrett brand hot dogs and the red onion sauce which Geisler created are the flagship products of Marathon Enterprises, Inc. The company is headquartered in Englewood, New Jersey.