In a small bowl, combine the mayonnaise, sriracha, and rice vinegar. Set aside.
In a separate small bowl, combine the soy sauce, rice vinegar, honey, garlic, and ginger. Heat the sesame oil in a large skillet over high heat. Add the salmon and sear for 90 seconds on all sides. Arrange the salmon skin-sides down, then pour the soy sauce mixture over the salmon. Cook until the sauce is slightly thickened, and the salmon easily flakes with a fork, about 3 minutes.
Divide the rice between bowls. Top with salmon, cucumber, avocado, nori, and sesame seeds, if using. Drizzle with remaining pan sauce and sriracha mayo before serving.