Yuzu (Citrus junos) is a small, knobbly, intensely aromatic East-Asian citrus, ripening from green to a rough yellow, with a perfume that suggests grapefruit, mandarin and a floral, almost herbal lift all at once. It yields relatively little sharp juice and a great deal of fragrant peel, so it is prized for its zest and a splash of juice rather than eaten as segments — the defining note of Japanese and Korean cooking, from ponzu and yuzu kosho to dressings, sorbets and the midwinter yuzu bath.