Cut the tuna into 1/4-inch (6 mm) dice for a classic crudo texture, or into 1/8–1/4-inch slices if you prefer carpaccio-style. Work quickly to keep fish chilled.

Make dressing

In a small bowl whisk together the olive oil, lemon juice, lemon zest, soy sauce, sesame oil, and a pinch (about 1/4 tsp) of the sea salt until combined.

Combine tuna and aromatics

Place the diced tuna in a medium bowl. Add the minced shallot, sliced scallions, and chives (if using). Pour the dressing over the tuna and gently fold to coat evenly. Taste and season with the remaining sea salt (totaling about 3 tsp) and freshly ground black pepper to your preference.

Rest briefly

Let the dressed tuna sit refrigerated for 5–10 minutes to allow flavors to meld, but do not marinate longer than 15 minutes so the fish remains pleasantly raw and firm.

Assembly & serving

Plate the crudo

Divide the tuna among 4 chilled plates (about 3 oz per serving). Arrange in small mounds or spread thinly across the plate according to your chosen cut.

Garnish and finish

Scatter microgreens or baby arugula around or atop the tuna, sprinkle the toasted sesame seeds, and add a few extra snips of chive and a little additional drizzle (about 1/2 tsp per plate) of olive oil if desired.

Serve

Serve immediately with crispy wonton chips or crostini on the side and lemon wedges. Advise diners to squeeze lemon to taste and eat promptly; the dish is best within 15 minutes of dressing.