How to Make It
In a small nonreactive saucepan, combine the soy sauce, sugar, ginger, lemon juice, orange juice, yuzu ponzu sauce and yuzu juice. Bring to a simmer, stirring until the sugar is dissolved. Remove from the heat and let cool completely.
In a medium saucepan, heat 1 1/2 inches of vegetable oil to 350°. Add the noodles and fry for 30 seconds, turning once with a slotted spoon until puffed. Drain the noodles on paper towels. Drizzle the noodles with sesame oil and season with salt. Gently break the noodles into 1-inch pieces and mound 2 tablespoons on each lettuce leaf.
Arrange the tuna slices on a large dinner plate and pour 1/4 cup of the Yuzu Ponzu over the fish. Let stand for 1 minute, then turn the fish and let stand for 1 minute longer. Set a tuna slice on each lettuce leaf and drizzle 1/4 teaspoon of the sauce on each leaf. Garnish each piece of tuna with a slice of jalapeño, a drop of Sriracha and a cilantro sprig and serve at once.