Rinse the sushi rice under cold water until the water runs clear, about 2–3 minutes. Cook rice according to package instructions or in a rice cooker.

While the rice is still hot, combine the rice vinegar, sugar, and salt in a small bowl and stir until dissolved. Pour over the hot cooked rice and gently fold to combine. Spread evenly into the bottom of a greased 9x13-inch baking dish to form an even layer. Set aside.

If using fresh salmon fillets, preheat oven to 400°F. Place the salmon on a lined baking sheet, season lightly with salt and pepper, and bake for 12–15 minutes until cooked through and easily flaked. Remove from oven and let cool slightly.

Flake the cooked salmon into a large mixing bowl using two forks, removing any bones or skin. If using canned salmon, drain thoroughly and add directly to the bowl.

To the bowl of flaked salmon, add the softened cream cheese, Kewpie mayonnaise, sriracha, soy sauce, sesame oil, and half of the sliced green onions. Stir well to combine until the mixture is creamy and fully incorporated.

Keep the oven at 400°F (or preheat if not already on). Spoon the salmon mixture evenly over the seasoned sushi rice layer in the baking dish, spreading it gently to the edges.

Drizzle the top generously with additional Kewpie mayonnaise and sriracha in a zigzag pattern.

Bake uncovered for 15–20 minutes, until the top is golden, bubbly, and lightly caramelized at the edges. Watch carefully in the last 5 minutes to avoid over-browning.

Remove from the oven and immediately top with the remaining sliced green onions, toasted sesame seeds, and tobiko if using.

Serve hot with nori sheets, sliced avocado, and cucumber on the side. To eat, scoop a generous spoonful of the salmon rice bake onto a nori sheet, top with avocado and cucumber, fold, and enjoy!