How to Make It
Preheat oven to 425°F. Coat a baking sheet with cooking spray. Stir together mayonnaise and shallot in a small bowl. Spread mixture evenly over mahi-mahi fillets to cover. Arrange fillets in an even layer on prepared baking sheet.
Stir together panko, tarragon, lime zest, salt, and pepper in a small bowl. Sprinkle mixture evenly over prepared fillets. Bake in preheated oven until panko is lightly browned and a thermometer inserted in thickest portion of fillets registers 140°F, 14 to 16 minutes.