Prepare the sushi rice: Rinse the sushi rice thoroughly under cold water until the water runs clear. Combine the rinsed rice, salt and water in a saucepan. Bring to a boil, then reduce the heat to low, cover, and simmer for about 15 minutes, or until the rice is tender and the water is absorbed
In a bowl, prepare the salmon-tuna filling by mixing chopped salmon, tuna, rice wine vinegar, soya sauce, spicy sauce and sliced green onion
Assemble the Sushi burrito: Lay a bamboo sushi rolling mat on a clean surface and place a sheet of plastic wrap over it. This will make it easier to roll the burrito. Wet your fingers with water to prevent sticking, and spread a thin layer of sushi rice evenly over the nori, leaving about an inch of nori uncovered at the top edge. Sprinkle sesame seeds over the rice
Arrange the sliced cucumber and avocado, salmon-tuna filling, Japanese mayo, pickle onions, pickle jalapeno and tobiko in the center of the rice
Carefully lift the edge of the bamboo mat closest to you, and begin rolling the sushi burrito away from you, applying gentle pressure to shape it. Use the plastic wrap to help lift and guide the burrito
Continue rolling until the nori and rice completely encase the fillings. Remove the plastic wrap and set the sushi burrito on a cutting board. Use a sharp knife dipped in water to slice the burrito in half