Light your charcoal in the KUDU and let them burn to embers with a layer of white ash.
In a small bowl, stir together the soy sauce, honey and sesame oil. Divide into two equal parts. Stir the rice vinegar into one part and set aside as a dipping sauce.
Spread the sesame seeds out on a plate. Coat the tuna steaks with the remaining soy sauce mixture, then press into the sesame seeds to coat.
Adjust your grill height over the ember at high heat. To locate high heat, place your hand over the embers and find the height you can count to 2 before having to remove your hand (approx. 600 degrees).
Move your KUDU cast iron to that height and add olive oil.
When the oil is extremely hot add tuna steaks, searing each side over high heat for less than a minute.
Remove and serve with the dipping sauce and wasabi paste.