Blot the 2 ahi tuna (yellowfin tuna) steaks dry and place them on a plate or in a resealable bag. The surface should feel dry to the touch so it can brown quickly instead of steaming.

Whisk the soy sauce, toasted sesame oil, honey, kosher salt if using, black pepper, and cayenne pepper until the honey disappears into the mixture, then coat both steaks well. For more flavor, marinate for at least 10 minutes or up to overnight in the refrigerator; reserve a little marinade before adding the fish if you want some for serving.

Heat a medium nonstick or well-seasoned cast iron skillet until very hot, using medium-high to high heat for cast iron and medium to medium-high heat for nonstick. Cast iron generally needs 3 to 5 minutes, while a nonstick skillet may need about 1 minute; a faint curl of smoke signals that the pan is ready.

Add the 1 tablespoon oil, then gently lay in the tuna and sear for 1 to 1½ minutes per side for medium-rare. For very rare tuna, cook about 30 seconds per side; for medium-well to well-done tuna, cook 2 to 2½ minutes per side, adjusting the heat if the glaze darkens too quickly.

Move the tuna to a cutting board and cut it into 1/2 inch slices, then finish with green onions, toasted sesame seeds, and lime wedges if desired. Serve right away while the center is warm and ruby colored; add flaky sea salt at the table if it needs more seasoning.