Pat the ahi tuna dry with paper towels. Season all sides lightly with kosher salt and freshly ground black pepper. Place the tuna on a plate and brush lightly with 2 tbs soy sauce and 1 tsp sesame oil; let rest for 5 minutes to absorb flavor.

Coat with sesame seeds

Spread the white and black sesame seeds on a shallow plate. Press each side of the lightly seasoned tuna into the seeds to create an even sesame crust on the exterior, leaving the center bare if desired for visual contrast.

Sear the tuna

Heat a heavy skillet (preferably cast iron) over high heat until very hot. Add 2 tbs neutral oil and swirl. When oil shimmers and is just beginning to smoke, carefully add the tuna. Sear 30–45 seconds per side for rare center (adjust to 60–90 seconds per side for medium-rare). Use tongs to sear the edges briefly to toast seeds. Remove tuna and transfer to a cutting board. Let rest 3–4 minutes before slicing thinly across the grain into 1/4-inch slices.

Salad Base

While tuna rests, assemble the salad base. In a large bowl, combine 6 cups mixed baby greens, thinly sliced half cucumber, sliced avocado, thinly sliced radishes, and sliced green onions. Toss gently to distribute ingredients evenly. Reserve a few avocado slices and radish rounds for garnish.

Dressing

Make the dressing: In a small bowl or jar combine 3 tbs low-sodium soy sauce, 2 tbs rice vinegar, 2 tsp sesame oil, 1 tbs fresh lime juice, 1 tsp honey, 1 tsp grated fresh ginger, 1/2 tsp minced garlic, and 1 tbs neutral oil. Whisk or shake vigorously until emulsified. Stir in 1 tbs toasted sesame seeds and season with 1/4 tsp freshly ground black pepper. Taste and adjust acidity or sweetness to preference.

Dress the salad lightly: Pour about half of the dressing over the salad base and toss gently to coat. Reserve the remaining dressing to drizzle over tuna and for guests to add more if desired.

Finishing & Plating

Plate the salad: Divide the dressed greens among two plates (or four smaller plates as an appetizer). Fan or arrange slices of seared ahi tuna atop each salad portion, overlapping slices for an attractive presentation.

Garnish and finish: Drizzle remaining dressing over the tuna slices. Scatter reserved avocado and radish slices, 2 tbs pickled ginger (optional), microgreens or 2 tbs cilantro, and a light sprinkle of toasted sesame seeds. Serve immediately with lime wedges on the side for squeezing.