A yuzu is about the size of a tangerine, and has a yellow-orange rind. The mature fruit produces little juice, and is mostly highly prized for its fragrant and floral zest, which combines the best flavors of lemon, mandarin orange, and grapefruit. The unripe fruit, with its green rind, does provide some juice, which is exceedingly sour yet delicious.
It's almost impossible to find fresh yuzu outside Japan, but bottled 100-percent yuzu juice-which is almost as good, and certainly more convenient-is becoming widely available in Asian markets, especially Japanese markets. A 10-ounce bottle costs around $12, but it will last a long time. Yuzu powder-dehydrated and pulverized yuzu zest-is also becoming easier to find. Googling "yuzu juice" will yield a list of online purveyors.
In Japan, yuzu zest is used mainly to accent cooked vegetables, hotpots, custards, and fish, and it's sometimes added to miso and to vinegar to infuse them with floral notes. Juice from green yuzu is often mixed with soy sauce to form a dipping sauce known as ponzu.
Use a teaspoon or so of yuzu juice-its flavor is quite intense-in braising liquids for fish and vegetables, or try combining it some with raw tuna and eat it spooned over good bread. Yuzu juice is also delightful mixed into a spoonful of miso, and then spread on fish and broiled. Or try a few drops (or more) in a salad dressing along with some good olive oil, yogurt, and maple syrup.
