For the coleslaw, very finely julienne all the vegetables. Place the daikon in a colander, sprinkle with salt and set aside for 15mins (this draws out some of the bitter juices.) Rinse the daikon and squeeze out excess water. Combine everything together.
Trim the tuna filet into a uniform baton, then rub crushed garlic all over. Season well with salt and pepper. Grill the tuna for a short time on all sides, keeping most of the center rare. You can use an open flame on a charcoal BBQ for the best flavour, or a kitchen blowtorch, or a non-stick pan. Set aside to rest.
Using a very sharp knife, slice the filet on an angle into thin slices. Should make about 8-10 slices in total.
Heap the coleslaw onto the center of a large round plate and drizzle with mayonnaise.
Arrange the tuna around the salad and drizzle with ponzu sauce.
