Make the Sushi Rice: Wash the rice with cold water until the water runs clear. Then add the rice and water to the rice maker. Cook according to the instruction. Once cooked, transfer the hot rice to a large bowl and let it cool down slightly. When it’s still very warm, stir in the sushi vinegar (or the mixture of rice vinegar, sugar, and salt).
Cut the Tuna: slice the tuna into 1/2-inch thick strips.
In a small bowl, mix together sriracha sauce and mayo to make spicy mayo.
Mix tuna strips with spicy mayo in a medium bowl.
Assemble Tuna Avocado Rolls: Lay out the bamboo mat with an optional piece of plastic wrap on top (this will make clean up easier).
Cut off 1/3 of the nori seaweed sheet using kitchen scissors.
Place the remaining nori sheet towards the bottom of the mat, shinning side facing down.
Take ¾ cup of cooked rice and evenly spread over nori. (You can dip your hands in Tezu vinegar water* to prevent sticking.)
Sprinkle with sesame seeds evenly on top. (I recommend toasting the sesame seeds first. Simply add them to a dry skillet on medium heat. Spread them evenly in the skillet and cook for about 5 minutes until lightly browned.)
Flip the rice covered nori sheet so that rice is facing down.
Place tuna strips and sliced avocado on top of the nori.
Place the thumbs underneath the bamboo mat and lift the edge up and over the filling.
Roll the bamboo mat away from you and apply some pressure to tighten it up. Keep rolling until the ends meet.
Once the roll is complete, move the roll to the cutting board and cut each roll into 8 pieces.
Serve with optional soy sauce, pickled ginger, and wasabi paste.