Preheat the oven to 375°F (190°C).

Rinse the sushi rice under cold water until the water runs mostly clear. Combine rice and 2.5 cups water in a rice cooker or saucepan. Cook according to rice cooker directions or bring to a boil, lower to a simmer, cover, and cook for 18 minutes. Let rest off heat for 10 minutes.

In a small bowl, stir rice vinegar, sugar, and salt until dissolved.

Fluff the cooked rice with a fork and gently fold in the vinegar mixture so the grains stay separate but glossy.

Spread the seasoned rice in an even layer across the bottom of a 9x13-inch (or similar) baking dish. Let the rice cool for 5 to 10 minutes.

In a medium bowl, combine diced salmon, mayonnaise, Sriracha, sesame oil, and chopped green onions. Mix until evenly coated. Taste and adjust Sriracha for spiciness.

Spoon or spread the salmon mixture evenly over the rice in the baking dish and smooth the top gently.

Bake for 25 to 30 minutes until the salmon is cooked through and the top shows light golden spots. If you want a more browned top, switch to broil for the final 1 to 2 minutes while watching closely.

Remove from oven and rest for 5 minutes. Garnish with extra green onions, nori strips, and tobiko if using. Scoop and serve warm.