Remove the tuna from the refrigerator about 20 minutes before cooking to take the chill off. Pat the steaks completely dry with paper towels, because surface moisture is the enemy of a good sear.

Combine white and black sesame seeds on a shallow plate or dish. Add the salt and pepper, then mix everything together with your fingers until evenly distributed.

Lightly brush each tuna steak with a thin layer of sesame oil. Press each side firmly into the sesame seed mixture, making sure to coat the edges as well for maximum crust coverage.

Whisk together soy sauce, rice vinegar, grated ginger, wasabi paste, and honey in a small bowl. Set aside to let the flavors meld while you cook the tuna.

Place your cast iron skillet over high heat for at least 3 minutes. You want this pan ripping hot because the brief sear time depends entirely on intense heat to create that crust without overcooking the interior.

Add the remaining sesame oil to the screaming hot pan. Immediately and carefully place the tuna steaks in the pan, then let them cook undisturbed for exactly 45 seconds to 1 minute.

Using tongs, flip the tuna and sear for another 45 seconds to 1 minute. If your steaks are thick enough, briefly sear the edges by holding them sideways with tongs for about 15 seconds per edge.

Transfer the seared tuna to a cutting board and let it rest for 1 minute. Using a very sharp knife, slice against the grain into 1/4 inch thick pieces to reveal that beautiful rare center.

Arrange the sliced tuna on plates in a fanned pattern. Serve immediately with the dipping sauce on the side and garnish with sliced scallions if desired.