Whisk together the soy, sesame oil, neutral oil, vinegar, honey and wasabi if using. Coat the tuna lightly for no more than 10 minutes — the tuna should taste like tuna, not marinade.
Heat a cast-iron or heavy pan over high heat until smoking hot. Remove the tuna from the marinade, pat dry and press sesame seeds onto all sides.
Sear 45–60 seconds per side. The goal is a crust outside and a rare center — don’t cook past medium-rare unless the tuna is lower quality.
Rest 2 minutes, then slice against the grain into ½-inch slices.
Drizzle with the remaining marinade or soy, sprinkle with scallions, crack fresh pepper over the top and serve with wasabi on the side.
Mediterranean variation (excellent with fresh tuna): season with olive oil, lemon zest, oregano and Reese Brand capers, and finish with flaky sea salt.
Good sides: sautéed spinach with garlic, sesame soba noodles or a simple cucumber salad.
