Yuzu is a sour Japanese citrus fruit, used both for its juice and its aromatic rind.
 
The yuzu (which is about the size of a tangerine) has an aroma and flavor that is distinct from any other citrus fruit, somewhat akin to a cross between grapefruit and lime.
 
Traditionalists will insist that many Japanese dishes are not authentic without this rare and hard to find juice!
 
This rare fruit is used in authentic Japanese cooking, common in seasoning meat, seafood dishes, sweets and beverages.