Baked Flounder with Roasted Tomatoes

Step 1

Preheat oven to 450°F, with racks in upper and lower thirds. Place tomatoes on a rimmed baking sheet. Drizzle with 1 tablespoon oil, and sprinkle with 1/4 teaspoon tarragon and the sugar; season with salt and pepper. Toss to coat. Arrange tomatoes in a single layer, cut sides up. Roast on lower rack until tender, 20 to 25 minutes.

Step 2

Meanwhile, make sauce: In a small bowl, whisk together mayonnaise, remaining 1/2 teaspoon tarragon, and the lemon juice; season with salt and pepper.

Step 3

Lightly oil another rimmed baking sheet. In a food processor, pulse bread with a pinch each of salt and pepper and remaining tablespoon oil until fine crumbs form.

Step 4

Pat fish dry with paper towels, and season both sides with salt and pepper. Place fillets on prepared baking sheet. Dividing evenly, spread mustard on top; sprinkle with bread crumbs, gently pressing to adhere. Bake on upper rack until fish is cooked through and coating is browned, 6 to 8 minutes. Serve with roasted tomatoes and sauce alongside.