Cook the sushi rice according to the package instructions. Combine rice vinegar and sugar in a small saucepan, warming gently until dissolved; mix with rice and set aside to cool.

Preheat your oven to 400°F (200°C) for even baking.

In a mixing bowl, combine cubed salmon with light soy sauce, Kewpie mayo, sriracha, and sesame oil until evenly coated.

Cut nori sheets into rectangles that will fit snugly in muffin tin cups.

Lightly spray the muffin tin with cooking spray, press nori sheets into each cup, fill with sushi rice, and top with the salmon mixture.

Bake in the oven for about 15 minutes until salmon is cooked and tops are golden brown.

Let the cups cool slightly, then garnish with extra sriracha or mayo, sprinkle with furikake and sliced green onions. Serve immediately.