Cook the Rice: Rinse the rice in a fine-mesh strainer under cold water until the water runs clear. Put the rinsed rice and 2.5 cups of water in a medium pot. Bring it to a boil, then immediately reduce the heat to the lowest setting, cover it, and let it simmer for about 15-20 minutes, or until all the water is absorbed. Take it off the heat and let it sit, still covered, for 10 more minutes.

Season the Rice: While the rice is resting, whisk together the rice vinegar, sugar, and salt until dissolved. Once the rice has rested, fluff it with a fork or rice paddle and gently fold in the vinegar mixture.

Prepare the Tuna: Pat the tuna loin dry with a paper towel. Using your sharpest knife, cut it into uniform 1/2-inch cubes. Place the cubed tuna in a medium, non-reactive bowl.

Make the Marinade: In a separate small bowl, whisk together the low-sodium soy sauce, sesame oil, grated ginger, and minced garlic. Pour this over the tuna. Add the sliced sweet onion and the white parts of the green onions. Gently toss everything together. Let it sit for at least 10 minutes, but no more than 30, in the fridge.

Assemble Your Poke Bowls: Divide the warm seasoned rice among four bowls. Spoon the marinated tuna over one side of the rice. Arrange your toppings—diced avocado, edamame, cucumber, and pickled ginger—around the tuna. Sprinkle everything with the green parts of the sliced green onions and sesame seeds. Serve immediately.