Cook sushi rice according to packaging instructions.
Set oven to 400℉.
Spray baking dish (see note about sizing below).
Using the largest holes (coarsest) on grater, grate the sriracha tofu.
Transfer tofu to medium bowl. Carefully combine grated tofu, vegan mayo, sea salt, lemon juice, and sriracha with spoon or fork.
Taste filling. Adjust seasoning as needed: sriracha for more heat, mayo for more creaminess, lemon for more brightness, sea salt for more savoriness.
Season cooked sushi rice with rice vinegar. Mix to combine.
Scoop rice into pan and pat down with spoon or wet fingers until even. If using a larger pan, leave approx. 1 inch around the outside. See photos above.
Now scoop filling out of bowl and on to sushi rice. Pat down until even.
Mix mayo, sriracha, and water into squirt bottle or small jar. Drizzle across sushi and save the rest for serving.
Sprinkle sesame seeds on top.
Bake for 13 minutes; topping will darken to pretty golden color.
Take sushi out of oven and allow to cool for 10 minutes.
Garnish with more green onion and avocado slices. If you want, you can use a damp paper towel to remove any sauce splotches from sides of pan (although cucumber and nori will cover them).
Add cucumber and nori sheets around sides. Serve with spoon and additional mayo/sriracha sauce and soy sauce on side.