Difference between Onion seeds and Nigella seeds
I found a recipe which calls for both onions seeds and nigella seeds. I spoke to someone at an Indian market, and he said nigella seeds and onion seeds are the same thing. The research I've done on the internet indicates the same. Does anyone know if they are different, or why a recipe would call for both if there isn't one?
They are different. True culinary onions are not at all related to Nigella species, though the seeds are remarkably similar in size, color and shape, but not ,most importantly, in flavor. They belong to entirely different plant families.
Because of the visual similarity, Nigella is often called by a nickname, Onion Seed.
Why a recipe would call for both Nigella seed AND onion seed is beyond me, unless perhaps it was translation error? I've not heard of Indian recipes calling for true onion seed as a flavoring.
Maybe an inquiry to a merchant online would get you a better answer.
I am not 100% sure they are the same, because my supermarket used to sell onion-flavored sprouts alongside the alfalfa sprouts. The tiny black seeds looked identical to Nigella/kalonji but had a potent onion flavor that the others don't seem to, unless the difference occurred via the sprouting process. I have never tried to sprout Nigella/kalonji.