In a colander, rinse the sushi rice several times until the water runs mostly clear.
In a medium saucepan or rice cooker combine rice and water. Cook according to the package directions.
In a small glass measuring cup, combine rice vinegar, sugar, and salt. Warm in microwave for 10-20 seconds until the sugar dissolves. Fold into rice and cool slightly.
For the Salmon
In a medium bowl, combine salmon, soy sauce, sesame oil, sriracha, garlic powder, and pepper. Toss until well coated.
Assembly
Preheat oven to 400 degrees. Grease muffin pan with nonstick cooking spray.
Cut each nori sheet into quarters. Place two in each cup.
Top with about 2 tablespoons of rice. Press into bottom and up the sides of the cup using damp fingers.
Top with salmon and bake for 15-18 minutes. Then broil for 1-2 minutes.
For the Spicy Mayo
Whisk all ingredients together.
Garnish
Allow the sushi cups to cool for 3–5 minutes. Garnish with avocado, green onions, sesame seeds, or cucumber if desired. Drizzle with spicy mayo.