Rinse the sushi rice under cold running water in a fine mesh strainer, working the grains gently with your fingers for 2–3 minutes until the water runs completely clear. The cloudy white water at the start is surface starch — left on the rice it produces an excessively sticky, clumped result rather than the glossy, lightly clingy texture that defines well-made sushi rice. Drain thoroughly after rinsing. Combine the rinsed rice and 540ml cold water in a medium, heavy-bottomed saucepan with a tight-fitting lid. Bring to a boil over high heat, then immediately reduce to the lowest possible heat setting, cover tightly, and simmer for exactly 15 minutes without lifting the lid at any point — the steam building inside the pot is doing the cooking, and releasing it at any stage produces uneven results. Remove from heat and let stand covered for a further 10 minutes. While the rice rests, combine the rice vinegar, sugar, and salt in a small bowl and stir until both are completely dissolved — undissolved sugar creates sweet spots in the finished rice. When the 10-minute rest is complete, uncover the rice and fluff gently using a rice paddle or fork with a cutting and folding motion rather than stirring. Pour the vinegar seasoning over the rice in a thin stream while continuing to fold — the goal is to coat every grain evenly while simultaneously fanning the rice slightly to help excess moisture escape and give the grains their characteristic gentle sheen. The finished rice should taste gently sweet-sour and look glossy. Keep covered and warm until assembly.

Ahi tuna is the correct and traditional fish for Hawaiian poke, and sushi-grade quality is the non-negotiable baseline. Ahi tuna — yellowfin or bigeye — should be deep red, almost burgundy in color when truly fresh, with an absolutely clean oceanic smell and a firm, dense texture. Any pink-grey coloration, soft texture, or even faint sour smell indicates fish that is not suitable for raw consumption. Buy from a reputable fishmonger and ask specifically when the fish arrived. Cut the tuna into uniform 1.5cm cubes — smaller than the salmon in a standard poke bowl because tuna's denser texture holds marinade differently, and the slightly smaller cube produces a better marinade-to-fish ratio and a more pleasant mouthful. In a medium bowl, whisk together the soy sauce, sesame oil, rice vinegar, grated ginger, and minced garlic until fully combined. The marinade is intentionally leaner than many poke marinades — no honey or additional sweetener — which allows the tuna's own clean, meaty flavor to remain the primary note rather than being sweetened. Add the cubed tuna and fold gently using a spatula, ensuring every piece is evenly coated without breaking the fish. Cover and refrigerate for 10–15 minutes. Tuna is denser than salmon and less susceptible to acid-cooking at the surface, but the 15-minute maximum still applies — beyond this the soy's salt begins to firm the fish noticeably.

In a small bowl, whisk together the Japanese mayonnaise, sriracha, and lime juice until smooth and fully incorporated. The lime juice is a small but important addition that distinguishes this spicy mayo from a simple sriracha-mayo combination — its citrus acidity brightens the rich, egg-heavy mayonnaise and sharpens the sriracha's heat into something more vivid and defined. Japanese mayonnaise, specifically Kewpie brand, is strongly preferred over Western mayonnaise — its higher egg yolk ratio, rice vinegar base, and slight umami note produce a fundamentally different and superior result in this application. Transfer to a squeeze bottle for controlled drizzling. If a squeeze bottle is unavailable, a small ziplock bag with one corner snipped works equally well and produces the same decorative drizzle effect. Refrigerate until assembly.

Place the sesame seeds in a dry skillet over medium heat and toast, stirring constantly, for 2–3 minutes until golden and fragrant. Sesame seeds go from raw to burnt quickly — watch continuously and remove immediately to a plate the moment they are golden. Toasted sesame seeds have a dramatically more complex, nutty flavor than raw ones and are worth the two minutes they require. Julienne the cucumber into thin matchsticks approximately 5cm long — unpeeled for color and textural contrast, or peeled for a cleaner appearance. Slice the radishes as thinly as possible, ideally on a mandoline, for the delicate translucent appearance that makes them visually striking in the bowl. Dice the avocados into generous cubes — slightly larger than the tuna cubes so they have visual presence alongside the fish. Shred the carrots on the large holes of a box grater. Slice the green onions thinly on a diagonal — the bias cut exposes more surface area and is both the visually correct cut and the most pleasant to eat in a raw garnish. Prepare the avocado last among the vegetables to minimize browning.

Divide the warm seasoned sushi rice evenly among four large, wide bowls — wide bowls are important because the visual presentation of a poke bowl depends on all components being visible simultaneously from above. Arrange the marinated tuna in an attractive mound in the center of each bowl, spooning any remaining marinade from the bowl over the fish to add additional flavor and gloss. Create distinct, separate sections around the tuna with the julienned cucumber, sliced radishes, diced avocado, and shredded carrot — each component occupying its own clearly defined space in the bowl rather than being mixed or scattered. This sectioned arrangement is the visual signature of a properly assembled poke bowl and is also practically important: it keeps the crisp vegetables separate from the moist fish so textures remain distinct until the moment of eating.

Drizzle each bowl generously with spicy mayo in a decorative zigzag pattern across all components. Sprinkle the toasted sesame seeds evenly from a height across the entire bowl surface. Add the sliced green onions and scatter the furikake seasoning over the top — furikake is a Japanese seasoning blend of dried seaweed, sesame seeds, and dried fish that adds an immediate oceanic, umami note connecting the bowl to its Hawaiian and Japanese heritage. Place a small portion of pickled ginger on the side of each bowl and a small amount of wasabi paste if using. Serve immediately — the essential eating experience of this bowl is the contrast between cold, clean marinated fish and warm, seasoned rice, and this contrast disappears as the bowl approaches room temperature.