Nigella seeds have a mild, nutty onion flavor, and they are used as a condiment in India and the Middle East on flatbreads and vegetable dishes. Their shape has an interesting appeal, edgier than sesame, but they can be used in many of the same ways. Give them a quick toast in a dry skillet to bring out the most flavor. Nigella seeds can be sprinkled on all manner of vegetable dishes and salads, from a simple stir fry to baked sweet potatoes.