Nobu's sashimi salad features partially cooked yellowfin tuna, a boon to anyone who doesn't enjoy completely raw fish. Nobu suggests serving this salad on just one plate. It's meant for sharing.
Season tuna all over with salt and pepper. Heat a nonstick skillet to high. Sear all 4 sides of fillet until cooked 1/4 inch on each side, 15 to 30 seconds each side. Transfer to a bowl of ice water and let cool; pat dry. Transfer to a cutting board and cut crosswise into 1/4-inch slices.
Slice carrot, zucchini, and beet into thin ribbons with a vegetable peeler. Toss with lettuce and scallion. Pour 1/4 cup dressing on a large lunch plate and top with a mound of lettuce mixture. Place tuna slices around lettuce mixture; serve.