In a bowl, combine the drained canned tuna, and add in mayonnaise, sriracha sauce, gochugaru chili powder, chopped green onion and sesame oil.

Give it a good mix and set aside.

Wash the short-grained sushi rice until the water runs clear.

Place washed rice into a rice cooker and cover with enough water.

In a small saucepan, combine the rice vinegar and sugar and bring to a simmer.

Give the mixture a stir until the sugar is completely dissolved.

Gradually pour the rice seasoning mixture over top of the rice and use a rice paddle to "cut" it through the rice, until thoroughly combined.

Use plastic wrap to wrap the bamboo sushi mat.

On a clean work surface, place the bamboo sushi mat along with a piece of nori seaweed shiny side down.

Take a portion of rice and flatten it onto the surface of the seaweed, leaving space on the top and bottom edges.

Sprinkle sesame seeds evenly on the rice.

Flip the seaweed sheet so the rice faces downward.

Add in about ⅓rd of the spicy tuna mixture, a few slices of cucumber and avocado.

Tightly roll up the seaweed, using the bamboo mat to shape it into a round log.

Assemble onto a plate and serve with wasabi, ginger and soy sauce, if desired.