Prepare the Tuna Mixture: In a medium bowl, whisk together ¼ cup mayonnaise, 2 tablespoons sriracha, 1 teaspoon sesame oil, 1 tablespoon soy sauce, and the juice of 1 lime until creamy. Gently fold in 8 ounces of diced sushi-grade tuna, ¼ cup finely diced red onion, and 2 tablespoons sliced green onion. Sprinkle in 1 tablespoon toasted sesame seeds. Cover and chill for about 15 minutes.

Fry the Wonton Shells: Heat about ½ inch of oil in a skillet over medium heat until 350°F. Fold each wonton wrapper into a taco shape and fry for 1 to 2 minutes each side until golden brown. Transfer to a paper towel-lined plate.

Assemble the Tacos: Spoon the chilled tuna mixture into each wonton shell. For added flavor, top with avocado, jalapeño slices, or pickled ginger.

Serve the Tacos: Arrange on a platter, sprinkle with sesame seeds and sliced green onions. Serve immediately.