I grew up on Long Island, NY, at a time when most of the bakeries were Jewish/German. Onion rye was a favorite, and readily found. No caraway in it. The loaf contained a swirl of the same dark brown, sweet, onion bits as top onion rolls and are part of the topping of “everything” bagels.
I have lived in the Boston area for 50 years. The NYC style deli is a rarity here, and the bakeries primarily Italian or Greek. I would have to drive closer or into Boston to have a chance of finding anything similar to authentic NYC rye, much less onion rye. Until 25 years ago, I visited metro NYC a few times a year and usually stopped in my old home town at one of its delis and bakeries. But by 2000, though most of the stores remained, owner ethnicity and therefore provisions sold, had changed. Onion rye is scrumptious. It’s always been puzzling to me that it isn’t made by all independent and major brand bread bakeries in the U.S.A.