In a medium-sized bowl, whisk together all of the ingredients except the cabbage. This can be done a day ahead of serving. For the crispiest salad, mix the grated or finely sliced cabbage with the dressing shortly before serving. The salad will look dry,
Blend all of the ingredients, except the tuna, in a food processor or blender, or mash them together using a mortar and pestle. Spread this paste over the tuna, reserving 2 tablespoons to brush onto the steaks after they've been cooked.
Grill (or saute) the tuna steaks just until blackened on the outside and cooked the way you like on the inside. Remove them from the heat, and brush with the remaining marinade. Cut into thin (about 1/4-inch) slices.
Heat 8 soft breads (See recipe:
) briefly, on the grill or in a frying pan, heating just till they're pliable and warm. Layer each with several slices of tuna, then top with slaw.