Season the tuna lightly with kosher salt and freshly ground black pepper on all sides. Brush the tuna loin with 1 tablespoon sesame oil to help seeds adhere.

Place the white and black sesame seeds on a shallow plate and press the tuna gently into the seeds on one face, then roll to coat the sides and top so the exterior is evenly covered (reserve one short edge uncoated if you plan to show a clean cut).

Heat a heavy-bottomed skillet or cast-iron pan over high heat until very hot (about 2–3 minutes). Add a teaspoon of neutral oil if pan is dry.

Sear the sesame-crusted tuna for 20–30 seconds per side for a rare center (adjust 45–60 seconds per side for medium-rare), using tongs to roll and sear each exposed face. Do not cook through; aim for a warm seared exterior and bright pink center.

Remove tuna from pan and transfer to a cutting board. Let rest 2 minutes while you finish the slaw and dressing.

Using a very sharp knife, slice the tuna across the grain into thin 1/8"–1/4" slices. Arrange slices over the prepared slaw just before serving.

Asian Vegetable Slaw

In a medium bowl combine the shredded green cabbage, red cabbage, julienned carrot, sliced green onion, chopped cilantro, and julienned cucumber.

In a small bowl or jar whisk together 2 tsp soy sauce, 2 tsp rice vinegar, 1 tsp sesame oil (for dressing), 1 tsp fresh lime juice, and 1 tsp honey or agave until the honey dissolves and the dressing is emulsified.

Pour most of the dressing over the slaw (reserve about 1 teaspoon for finishing the plate). Toss gently to combine so the vegetables are evenly coated but still crisp. Taste and adjust seasoning—add a pinch of salt or more soy if desired.

Dress the plate with the reserved teaspoon of dressing and, if desired, a drop (1/2 tsp) of toasted sesame oil for aroma right before plating.

Assembly & Garnish

Arrange a loose mound of the dressed Asian vegetable slaw on each appetizer plate or a single shared board if serving tapas-style.

Fan the thinly sliced sesame-seared tuna over the slaw so each piece rests partially on the vegetables.

Dot or drizzle the wasabi mayo (about 2 tablespoons total) over the tuna in small spoonfuls or a thin zigzag. If you prefer heat, mix a little extra sriracha into the mayo.

Sprinkle remaining toasted or untoasted sesame seeds lightly over the tuna and slaw for extra crunch.

Garnish with microgreens or additional chopped cilantro and place pickled ginger to the side. Serve with lemon or lime wedges so guests can squeeze fresh citrus if desired.

Serve immediately while tuna is still warm at the edges and the slaw is crisp.