Slice all the vegetables thinly with a very sharp mandoline and put them in icy water for about an hour. Combine marinade ingredients. Cut the tuna in a long thin slices about 1/2-inch thick and let sit in the marinade for about 20 minutes. In a medium size skillet over high heat sear the tuna briefly, until rare. Reserve on the side once done. Drain all the vegetables, dry them and season with a little bit of lemon and olive oil seasoned to taste. Place a small amount in the middle of the plate and add the thin slice of tuna on top of it. Combine tapenade dressing and drizzle vinaigrette on tuna.