To make the salmon fillet, drain the tofu and carefully squeeze out as much moisture as you can using a clean tea towel, ensuring you don't break the structure of the tofu. Slice the brick into 2 (5 ½ x 2-inch) fillets. I think it will depend on the shape of your brick, but I found it best to cut it diaginally to get as close to a realistic shape as I could. I also trimmed off the sharp corner on the thickest edge to make it look more like a real salmon fillet.
Place a chopstick on either side of the tofu fillets (longest side) and use a sharp knife to score partway through the fillets and down the entire length.
In a deep dish, mix together the beet juice, water, lemon juice, vegan fish sauce or soy sauce, and sea salt. Submerge the tofu fillets in the marinade and leave to marinate for at least 4 hours. Drain and pat the tofu filets dry with a paper towel.
Fill a shallow bowl with water and potato starch and whisk together.
Slice the nori and rice paper each into 2 rectangles the same width and one third longer in length as the top of the tofu fillets. I found this easiest to do by layering the nori on top of the rice paper sheet. Place the tofu fillets top down onto the nori and then cut with a sharp knife around it. The reason you make the strips longer than the fillets is that it shrinks so much when you fry them. The nori will probably stick to the tofu fillets which is fine. Use your finger to gently press it on the tofu.
Dip the rice paper strip in the water and potato starch mixture for a few seconds or until just softened, then lay them on top of the nori. Use a pastry brush to brush the remaining potato flour mixture over the exposed parts of the tofu fillets.
Heat a large cast iron or nonstick frying pan over medium heat with vegetable oil. When hot, place the tofu fillets in the pan, rice paper side down first and fry until crispy and browned, about 2 to 3 minutes. Flip and fry the bottom for 2 to 3 minutes more, then repeat on each side of the fillets.