Instructions

For the Branzino and Potatoes: Adjust oven rack to middle position and heat oven to 425 degrees. Line rimmed baking sheet with parchment paper. Toss 1 pound halved small red potatoes with 2 tablespoons vegetable oil and ½ teaspoon table salt. Arrange on prepared sheet, cut sides down, and roast 25 minutes.
 For the Curry Mayonnaise: Meanwhile, combine ¾ cup mayonnaise, 1 tablespoon lemon juice, 1 tablespoon curry powder, ½ teaspoon garam masala, 1 tablespoon water, ¼ teaspoon salt, and 2 tablespoons minced cilantro in bowl. Season with extra salt to taste. Cover and refrigerate until ready to serve.
Combine remaining 1½ teaspoons salt, ½ teaspoon pepper, 1 teaspoon garam masala, and ¼ teaspoon cayenne pepper in bowl. Rinse 2 whole branzino, scaled, gutted, and fins snipped off with scissors, under cold running water and pat dry with paper towels inside and out. Using sharp knife, make 3 or 4 shallow slashes, about 2 inches apart, on both sides of branzino. Open cavity of branzino and sprinkle ½ teaspoon salt mixture on flesh in each. Stuff each cavity with ½ thinly sliced lemon. Brush remaining 2 tablespoons oil on outside of branzino and season outside of each with additional ½ teaspoon salt mixture; transfer to plate and let sit for 10 minutes.
Remove baking sheet from oven. Increase heat to 500 degrees. Move potatoes to one side of sheet and arrange fish on other side. Roast until branzino flakes apart when gently prodded with paring knife and registers 140 degrees, 15 to 20 minutes.
Carefully transfer branzino to platter and let rest for 5 minutes. Toss potatoes with remaining 1¼ teaspoon salt mixture and transfer to platter.
Fillet branzino by making vertical cut just behind head from top of fish to belly; discard lemon slices. Make another cut along top of branzino from head to tail. Use spatula to lift meat from bones, starting at head end and running spatula over bones to lift out fillet. Repeat on other side of branzino. Discard head and skeleton. Serve with curry mayonnaise and potatoes.