In a medium saucepan, combine the sushi rice and water. Bring it to a boil over medium-high heat, then reduce the heat to low, cover, and simmer for about 15-20 minutes, or until the water is absorbed, and the rice is tender.
Add the hot rice to a bowl and fill a cupcake baking pan with it and use a tablespoon to press it down.
Freeze the pan for about 30 minutes.
Spray the rice with olive oil and bake the rice at 180 degrees till crispy and golden.
In a bowl, add in the canned tuna, mayo, and siracha. Mix them well.
Fill the rice cups with the tuna mixture and top with sesame seeds and avocado slices!