Preheat oven to 400°F (205°C). Pat the branzino dry inside and out with paper towels. Season the cavity and exterior lightly with 1 tsp of the salt and 1/2 tsp of the black pepper.

Make the stuffing

In a medium bowl combine chopped parsley, chopped dill, minced garlic, minced shallot, lemon zest, chopped capers, breadcrumbs, 2 tablespoons olive oil, dry white wine, remaining 1/2 tsp salt, red pepper flakes, and a pinch of freshly ground pepper. Mix until just combined; stuffing should be moist but not soupy. Add a splash more olive oil or a teaspoon of water if too dry.

Stuff the fish

Loosely fill each branzino cavity with about half of the stuffing mixture so the fish hold shape but air can circulate. Tuck a couple of lemon slices into each cavity on top of the stuffing. Use kitchen twine to truss the tail to the head or secure with toothpicks if desired.

Oil and season exterior

Brush the outside of each stuffed branzino with the remaining 1 tablespoon olive oil and season the exterior with remaining 1/2 tsp salt and a light grind of black pepper.

Roast Vegetables & Finish

Prepare vegetables

Place halved baby potatoes and cherry tomatoes on a rimmed baking sheet or in a shallow roasting pan. Toss with 2 tablespoons olive oil, 1 tsp sea salt, and 1/2 tsp black pepper. Spread into an even layer, leaving room in the center or one side of the pan for the fish.

Arrange fish and roast

Place the stuffed branzino on the baking sheet among the vegetables (or on a rack set over the vegetables). Add lemon slices around the fish. Roast in the preheated oven for 20–25 minutes, or until the fish flesh flakes easily with a fork and reaches an internal temperature of 135–140°F (57–60°C) at the thickest part. Potatoes should be tender and golden; tomatoes should be blistered.

Rest and finish

Remove the pan from the oven and let the fish rest for 3–5 minutes. Spoon any pan juices over the fish and vegetables. Sprinkle the chopped parsley over the entire dish and, if desired, squeeze fresh lemon juice over the fish before serving.

Serving suggestion

Transfer the stuffed branzino to a serving platter with the roasted potatoes and tomatoes. Serve hot with extra lemon wedges on the side.