In a large bowl, season the cooked sushi rice with rice vinegar, sugar, and salt, stirring gently until combined.
Preheat a waffle iron and brush with sesame oil to prevent sticking.
Place a layer of seasoned sushi rice on the waffle iron, spreading evenly to cover the surface. Close and cook for 5-7 minutes, or until the rice is golden and crispy.
In a small bowl, mix mayonnaise and sriracha to create a spicy sauce.
Carefully remove the rice waffle and top with avocado slices, cucumber, and smoked salmon or tuna. Drizzle with spicy mayo and a touch of soy sauce.
Garnish with nori strips, sesame seeds, and green onions. Serve immediately.
Notes
Ensure the rice is cool before using it in the waffle iron to prevent it from becoming too sticky.