First start with the marinade, add all the marinade ingredients into a small bowl and mix well to combine. Taste it and see if you want to add any more of the ingredients to the sauce. Then place the Ahi Tuna steak in a large ziplock bag and pour the marinade over the top. Then move the bag all around to make sure it is coated evenly. Place in the refrigerator for a few hours or as long as you have.