Sauce: Char peppers over gas flame or under broiler until blistered on all sides. Enclose in a paper bag and let stand 15 minutes. Peel peppers, remove stem and seeds, and dice. Measure 1/4 cup diced peppers into a small bowl and add mayonnaise, sour cream, cilantro, lime juice, ginger, garlic, and salt; stir well.
Burgers: Meanwhile, in large bowl, beat egg and stir in panko, soy sauce, sugar, sesame oil, ginger, garlic, lime juice and zest, red pepper flakes, and salt. Add ahi and combine gently; form 4 patties.
Heat vegetable oil on nonstick griddle over medium-high heat. Add patties and cook 3 to 4 minutes per side. Toast rolls under broiler during last few minutes of cooking. Spread sauce on roll bottom and top with onion, tomato, sprouts, and additional sauce. Add roll tops and devour.