Preheat your oven to 375°F. Rinse the sushi rice under cold running water until the water runs clear to remove excess starch. Cook according to package directions (usually 15-20 minutes), then let it rest covered for 10 minutes off the heat.

While the rice cooks, combine rice vinegar, sugar, and salt in a small bowl, stirring until completely dissolved. Set aside. Once rice is done, transfer it to a large bowl, drizzle the vinegar mixture over top, and gently fold it in using a cutting motion with your spoon or rice paddle.

Spread the seasoned rice evenly across the bottom of a 9x13 inch baking dish, pressing it down gently with the back of a spoon. Let it cool for 5-10 minutes while you prepare the salmon topping.

In a mixing bowl, combine the diced salmon, mayonnaise, Sriracha, sesame oil, and green onions. Mix until everything is well coated. Taste and adjust the spice level if needed. The mixture should be creamy but not soupy.

Spread the salmon mixture evenly over the rice layer. Bake for 25-30 minutes until the salmon is cooked through and edges start to turn golden. The salmon should be opaque and flake easily when tested with a fork, with an internal temperature of 145°F. For extra color and crispiness, you can switch to broil for the last 2-3 minutes, watching closely to prevent burning.

Remove from the oven and let it rest for 5 minutes. Garnish with additional green onions, nori strips, and tobiko or furikake if using. Serve warm by scooping portions into bowls.