Place the tuna steaks in a medium-size bowl. Set aside.
To make the marinade: Combine all marinade ingredients in a small bowl.
Pour the marinade over tuna steaks until they’re well-coated. Cover with plastic wrap and allow to marinate for at least 15 minutes at room temperature.
In a large skillet over medium-high heat, add cooking oil, tuna steaks, and marinade. Cook for about 2-3 minutes on each side or until done.
Transfer sauteed tuna steaks to a clean plate. Sprinkle with sesame seeds.
Serving Suggestions: Serve this dish with steamed broccoli or a green salad.