Combine the soy sauce, green onions, lemon juice, garlic, and sesame oil in a bowl and whisk together well.
Add your ahi tuna steaks to a large plastic bag. Pour all of the marinade (except for 1/4 cup we’ll save for later) you just whisked together into the bag and seal it tight, pressing out all of the air as you do so.
Lay the bag flat and make sure the marinade is coating all of the tuna steaks. Let them marinate for about 30 minutes.
Spread the sesame seeds on a plate in a flat even layer. Remove the tuna steaks from the bag and press each one into the sesame seeds making sure all sides are coated.
Now, it’s time to grill! Spray your grill grates with cooking oil spray. Preheat the grill to high heat. For rare ahi tuna steaks, once the grill is heated, grill the steaks for about 3 minutes on each side.
Once cooked, garnish with additional green onions and the leftover marinade and enjoy!
The nutrition facts presented here are estimates only. The brands you use and product types chosen can change the nutritional information presented. To obtain the most accurate nutritional information, you should calculate the nutritional information with the actual ingredients you use.