Cut tune steak into bite sized pieces and set aside.Add marinade to a bowl and toss in the tuna.
Place plastic wrap over the bowl pressing it against the tuna and place in fridge of 2+ hours.Slice up cucumber and avocado and set aside.Add cabbage to a bowl drizzle with sesame oil and rice wine vinegar and toss.
Place cucumber and avocado on top.Once tuna has been marinating for at least 2 hours remove from bowl leaving excess marinade in bowl and place on top of cabbage.Top with sesame seeds, sushi nori and scallions.
Serve cold and enjoy!