Soy mirin dressing
1.Cook noodles in large saucepan of boiling water until tender; drain. Rinse under cold water; drain.
2.Make soy mirin dressing. Place ingredients in screw-top jar; shake well.
3.Place cold noodles in large bowl with ginger, onion and three-quarters of the dressing; toss gently to combine. Cover; refrigerate until chilled.
4.Cook tuna on heated oiled grill plate (or grill or barbecue) until just cooked (do not overcook tuna or it will dry out).
5.Divide noodle salad among serving dishes; top with tuna, drizzle with remaining dressing and sprinkle with seaweed.