01 - Rinse the sushi rice under cold water until the water runs clear. Combine rice and water in a saucepan, bring to a boil, then cover and simmer on low for 18 minutes. Remove from heat and let stand, covered, for 10 minutes.
02 - In a small bowl, mix rice vinegar, sugar, and salt. Gently fold this mixture into the cooked rice. Let cool to room temperature.
03 - In a medium bowl, whisk together the mayonnaise, Sriracha, sesame oil, soy sauce, and lime juice. Add the diced tuna and toss gently to coat. Keep chilled until ready to serve.
04 - In a small bowl, mix soy sauce, rice vinegar, honey, and sesame oil to make the dressing.
05 - Divide the seasoned rice among four bowls. Arrange spicy tuna, mango, avocado, cucumber, carrot, and pickled ginger (if using) on top.
06 - Drizzle with soy dressing. Garnish with spring onions, sesame seeds, crispy onions, and nori strips. Serve immediately.