Rinse sushi rice until the water runs clear. Prepare the rice according to package instructions. While cooking, in a small bowl whisk together rice vinegar, sesame oil, salt, and sugar until combined. Pour the mixture on your cooked rice and mix.
In a 8×8 baking dish, add the rice, pressing down firmly and evenly with a spatula, then sprinkle with half of the furikake seasoning. Set aside.
Preheat the oven to 400 degrees F.
Shred the salmon and place it into a bowl. Add in the green onions, cucumber, Kewpie mayo, sriracha, and soy sauce. Mix the ingredients together until combined.
Spread the salmon mixture evenly on top of the rice. Sprinkle with the remaining furikake seasoning.
Bake for 10 minutes then broil for 2-3 minutes until the top has darkened slightly.
Remove from the oven and drizzle with more mayo and sriracha over the sushi bake; then sprinkle with extra chopped green onions. Serve warm on nori sheets.