As the rice cooks, add ice water to a large bowl and set it aside. Now, bring another small pot of water to a boil. Rinse the tomatoes before piercing them with a knife. Now, drop them into the boiling water for 30–45 seconds, until the skins start loosening. Immediately transfer to the ice bath to stop cooking. Peel off the skins once cool.

Take a container that has a lid. Add soy sauce, ginger, kelp powder, sriracha, and sesame oil and stir until it's all combined.

Peel the cooling tomatoes. Scoop out the seeds and dice the tomato flesh into small pieces. Add these pieces to the container with the marinade. Place the lid on top and give the container a good shake, ensuring all pieces are evenly coated.

Cut the cucumber and avocado into thin slices (like matchsticks). Now, prepare a sushi rolling station by laying out a kitchen towel on a counter (or cutting board). Add a sheet of plastic wrap on top of the towel.

Place a nori sheet (shiny side down) on the plastic wrap. Gently dab your fingers with water. With wet fingers, spread a layer of sushi rice on the nori. Make sure the layer is very thin. Leave a little space (an inch) on both ends of the sheet to wrap it.

Arrange the marinated tomato, cucumber, and avocado in a horizontal line near the bottom edge. Make sure the toppings only cover 2 inches of the rice, or else you won’t be able to roll the sushi.

Gently roll the edges of the Nori sheet, covering the vegetables. Once covered, roll over the plastic wrap and then the kitchen towel. Using a sharp, wet knife, cut the roll into bite-sized pieces. Serve with soy sauce, wasabi, and pickled ginger.