Creating Spicy Tuna Onigiri is straightforward if you follow these steps:

1. Prepare Sushi Rice: Rinse the sushi rice under cold water until the water runs clear. Drain well.
2. Cook Rice: In a pot, combine rinsed rice with water. Bring to a boil, then reduce heat to low, cover, and simmer for 20 minutes or until water is absorbed. Remove from heat and let it sit covered for 10 minutes.
3. Season Rice: In a small bowl, mix rice vinegar, sugar, and salt until dissolved. Gently fold this mixture into the warm rice. Let it cool until it can be handled.
4. Make Spicy Tuna Filling: In a bowl, combine diced tuna, mayonnaise, sriracha, sesame oil, and chopped green onions. Mix until well combined and set aside.
5. Shape the Onigiri: Moisten your hands to prevent sticking. Take a handful of rice (about one-third cup) and flatten it slightly in your palm. Place a spoonful of the spicy tuna filling in the center.
6. Mold the Rice: Carefully fold the rice over the filling, shaping it into a triangle or round shape. Press gently but firmly to hold the shape.
7. Wrap with Nori: Cut nori sheets into strips and wrap them around the base of each onigiri for added flavor and texture.
8. Optional Garnish: Sprinkle sesame seeds or serve with avocado slices on the side, if desired.
9. Chill or Serve: You can serve immediately or refrigerate until needed, allowing the flavors to meld.

These clear steps provide an easy guide to making your very own Spicy Tuna Onigiri at home!