In a large mixing bowl, whisk together mayonnaise, sriracha, sesame oil, soy sauce, and fresh lime juice until well-combined. Carefully fold in the diced sushi-grade tuna, chopped red onion, green onion, and a sprinkle of toasted sesame seeds. Cover with cling film and refrigerate for at least 15 minutes.

In a deep skillet, heat about an inch of oil over medium-high heat until it reaches 350°F (175°C). Carefully mold each wonton wrapper into a taco shape using a taco mold or by pressing them into the oil with a slotted spoon. Fry for about 1-2 minutes on each side until golden brown and crispy. Transfer to a paper towel-lined plate to drain excess oil.

Once the wonton shells have cooled, fill each shell generously with the chilled spicy tuna mixture. Layer slices of ripe avocado on top. Sprinkle additional sesame seeds or your choice of toppings like jalapeño slices or pickled ginger.

Plate the assembled Spicy Tuna Tartare Wonton Tacos and garnish with sesame seeds and sliced green onions. Serve immediately for a satisfying crunch.