This herb is a common ingredient in Vietnamese cooking, and the name describes both its fragrance and look: the scent is intensely lemony (more like the smell of zest than fruit), and the plant looks like a wild grass. In the markets, what you get is a tight bulb that extends into a firm stalk. The prized portion is the bulb, but you must peel away a couple of the rough outer layers to get to the best part. You must also lightly crush the bulb or finely chop it to release its full flavor and aroma. While most recipes tell you to discard the stalk, I save it, cut it into inch-long pieces, and steep it with fresh ginger and honey to make an invigorating tea that is good hot or cold.