Place tuna in shallow pan and pour marinade over them. Set aside for 15 minutes.
In medium bowl, toss cabbage, snow peas and carrots with 3/4 C. dressing.
Heat a grill pan or large cast iron skillet over high heat. Coat pan with vegetable oil.
Pat sesame seeds onto tuna.
Sear tuna on both sides for about five minutes per side, depending on how rare you like the tuna.
Divide the slaw on four large salad plates.
Cut the tuna into thin slices and fan out onto side of plate. (4 oz. tuna steaks serve one per plate, 8 oz. tuna steaks, divide each portion into two servings).
Drizzle with remaining dressing. Garnish with green onion