Season each Ahi steak with sea salt and pepper, then brush with a nice Dijon mustard, and press mustard side down into a plate of sesame seeds.
Heat a little sesame oil (just enough to lightly coat the pan) in a large pan, until it begins to smoke. (Hint— have the oven fan running before you start; the smoke alarm will make you jump) and carefully lay the tuna seeds-side down in the hot oil.
Count to 30, and then carefully flip the tuna over. Cook for another 30 seconds, and remove it to a plate to serve. Whisk a little wasabi past in into a 1/4 cup of mayonnaise for a quick Wasabi Aioli, which pairs perfectly with the tuna.