Rinse sushi rice under cold water until clear. Cook according to package instructions or boil in about 2 cups of water until tender, then fluff with a fork.

In a bowl, mix rice vinegar, sugar, and salt. Fold this mixture into the warm rice.

Marinate diced tuna in soy sauce and sesame oil for about 10 minutes.

In serving bowls, layer seasoned rice first, followed by marinated tuna and desired toppings (avocado, cucumber, green onions).

Drizzle with extra soy sauce or sesame oil before serving.