Cook the sushi rice according to package instructions until fluffy, then let cool slightly.
Combine rice vinegar and sugar in a microwave-safe bowl, heat until sugar dissolves, then mix with sushi rice.
Preheat your oven to 400℉.
Mix diced salmon with light soy sauce, Kewpie mayo, sriracha, and sesame oil until well-coated.
Cut nori sheets into squares, place sushi rice in muffin tin, and add salmon on top.
Bake for about 15 minutes until salmon is cooked and tops are golden brown, then garnish before serving.