Make the soy-ginger glaze: In a small saucepan combine the soy sauce, mirin, honey, grated ginger and minced garlic. Bring to a gentle simmer over medium heat, then reduce heat to low and simmer 4–6 minutes until glossy and slightly reduced. Why: reducing concentrates and balances the sweet-salty flavors and slightly thickens the glaze so it will cling to the tuna rather than run off.

Toast the sesame seeds: Heat a dry skillet over medium heat, add the sesame seeds and toast, stirring constantly, 2–3 minutes until fragrant and lightly golden. Remove to a plate to stop cooking. Why: toasting blooms the oils in the seeds and deepens their nutty flavor — plain seeds taste flat in comparison.

Quick-pickle the cucumber: In a bowl whisk rice vinegar, sugar and 1/2 tsp salt until dissolved. Add thinly sliced cucumber and 2 tablespoons sliced scallions; toss and let sit at room temperature while you cook (minimum 10 minutes). Why: a short pickle brightens the cucumber with acid and sugar, adding crunch and cutting the richness of tuna and coconut rice.

Make the coconut jasmine rice: Rinse the jasmine rice under cold water until the water runs almost clear to remove excess surface starch — this prevents gummy rice. Combine the rinsed rice, coconut milk, water, and a pinch of salt in a medium saucepan. Bring to a boil, then reduce to the lowest heat and cover tightly; simmer 12–14 minutes until liquid is absorbed. Remove from heat and let rest, covered, 10 minutes. Finish by stirring in 1 tbsp cold butter and fluffing with a fork. Why: low, gentle heat and a rest period produce separate, tender grains; the butter adds creaminess and sheen.

Prepare the tuna: Pat tuna steaks dry with paper towels (moisture prevents proper crust). Season all over with 1 tsp kosher salt and 1 tsp black pepper. Brush lightly with the 1 tbsp sesame oil. Why: drying ensures a good sear; sesame oil gives a layer of flavor that helps the sesame seeds adhere.

Press the tuna into the sesame: Spread the toasted sesame seeds on a cutting board or shallow plate. Press each seasoned tuna steak firmly into the seeds, covering the top and sides — do not coat the bottom (that side will be pan-seared to make a neat crust). Why: this creates a crunchy, flavor-packed exterior while keeping the underside bare so it makes full contact with the hot pan.

Sear the tuna: Heat a large heavy skillet (cast-iron preferred) over high heat until very hot. Add the neutral oil and swirl. Place tuna steaks seed-side down first (so seeds make contact with the hot oil) and sear 30–45 seconds without moving until seeds form a golden crust. Flip and sear the other side 30–45 seconds for rare (internal temp ~115–120°F / 46–49°C). Reduce or increase time if you prefer more or less doneness. Why: high heat gives a quick Maillard crust on the exterior while keeping the center buttery-rare; tuna quickly overcooks — short sear times are key.

Rest and glaze: Transfer tuna to a plate and let rest 3 minutes (carryover heat evens the temperature). Spoon the warm soy-ginger glaze over the top or brush lightly to coat. Why: resting relaxes the juices and lets the glaze adhere rather than run off when you slice.

Finish pickles and rice: Drain most of the quick-pickle liquid if you prefer less wetness, toss the cucumbers again with remaining scallions and a squeeze of lime. Fluff the coconut rice once more and keep warm. Why: draining prevents watering down the plate and concentrates flavor.

Slice and plate: Using a sharp chef’s knife, slice tuna against the grain into 1/4–1/2-inch thick slices. Spoon a bed of coconut jasmine rice onto each plate, fan tuna slices alongside, spoon extra glaze over the tuna, and add a small mound of pickled cucumber. Garnish with remaining scallions and cilantro or microgreens and a drizzle of olive oil if you like. Why: slicing against the grain shortens the muscle fibers for a more tender bite; plating builds contrast in texture and temperature for an elegant presentation.

Serve immediately: This dish is best served right away so the tuna retains its rare center and crunchy sesame texture; the warm rice and cool pickles are meant to be eaten together on the first bite. Why: delays will soften the crust and change the ideal temperature contrasts.