My Friend and I just stopped here. They do NOT have a GL menu at all (but staff was very kind). Not recommend for GF people. Sorry.
John will make you an Amberger Salad that is GF. You will get a hamburger (with no bun), lettuce, tomato, onion, ketchup and mustard. He uses all fresh utensils to make it and cooks it separately on foil. He serves potato chips with it.