Cook the rice: Rinse sushi rice under cold water until water runs clear. Combine rice and water in a pot, bring to a boil, then reduce heat to low, cover, and simmer for 15–18 minutes until water is absorbed. Remove from heat and let sit, covered, for 10 minutes.

Season the rice: In a small saucepan, combine rice vinegar, sugar, and salt. Heat over low heat, stirring until sugar and salt dissolve. Let cool slightly. Transfer warm rice to a large shallow dish, drizzle vinegar mixture over, and gently fold to combine. Fan or let cool to room temperature.

Prep for baking: Preheat oven to 375°F (190°C). Grease a 9×9‑inch or 9×13‑inch baking dish. Press seasoned rice evenly into the bottom of the dish.

Make spicy salmon mixture: In a large bowl, combine cubed salmon, softened cream cheese, mayo, sriracha, soy sauce, and sesame oil. Mix until salmon is evenly coated.

Assemble the bake: Spread spicy salmon mixture evenly over the rice layer. Sprinkle shredded mozzarella on top if using.

Bake: Bake for 20–25 minutes, until salmon is cooked through and cheese is bubbly and lightly golden.

Broil (optional): Switch oven to broil for 1–2 minutes to crisp the top slightly. Watch closely to prevent burning.

Garnish and serve: Remove from oven and top with sliced green onions, furikake, and sesame seeds. Serve warm with nori sheets, cucumber slices, or rice crackers for scooping. Add avocado slices just before serving.