Ponzu is a blend of a few essential Japanese ingredients - mirin, rice wine vinegar, yuzu, kombu (seaweed) and bonito (dried tuna) - and the result is as complex and nuanced as the list of ingredients would suggest.
The flavor is at once, sweet, tart and savory. It is almost always blended with soy sauce to create the umami flavors so sought after in Japanese cuisine. This mixture is a perfect dipping sauce for raw fish, steamed dumplings or raw vegetables like radishes and fennel.
A drizzle of ponzu into a steaming bowl of noodles is a nice addition. You can make a quick dressing for a vegetable slaw with carrots and cabbage with ponzu and soy sauce. It also makes a great pan sauce - after cooking pork or chicken that's been pounded thin, deglaze the pan with a 1/2 cup of ponzu and a splash of shoyu - the sugars will caramelize as the mixture reduces and you'll have a lovely sauce.
Ponzu also makes a great quick marinade for fish. Julienne some ginger and toss with ponzu and marinate salmon filets for 30 - 45 minutes. Cook the fish and then reduce the marinade and serve alongside or drizzled over the fish.