This roasted branzino recipe is a simple, hands-off way to make whole roasted branzino at home - stuffed with lemon, garlic, red onion, and fresh herbs, then roasted until tender and finished under the broiler for perfectly crisp, edible skin and easy-to-remove bones.
Rinse each branzino under cold running water, then pat dry with paper towels inside and out. Open cavity of each branzino and sprinkle ¼ teaspoon each of salt and black pepper on the flesh.
Adjust oven rack to middle position and heat oven to 475 degrees F. Line rimmed baking sheet with parchment paper and grease parchment with 1 Tablespoon of the olive oil.
Stuff each branzino cavity with 1 teaspoon minced garlic, 2 slices of lemon, 2 sprigs thyme, 2 sprigs rosemary, and some sliced red onion. Brush 1 Tablespoon oil on the outside of each branzino, then sprinkle with a little more salt.
Roast until branzino flakes apart when gently prodded with a fork and registers an internal temperature of 135 degrees F, about 15 minutes. Turn on the broiler and cook until skin is crispy and internal temperature reaches 140 degrees, about 3 minutes.
Carefully transfer branzino to cutting board and let rest for 5 minutes. Fillet branzino by making a vertical cut just behind head from the top of the fish to the belly. Make another cut along top of branzino from head to tail. Use a fish spatula to lift meat off of the bones, starting at head end and running spatula over bones to lift out fillet. Repeat on other side of branzino. Discard the head and skeleton, as well as the lemon and onion slices.
Season each branzino fillet with a small sprinkle of salt and pepper and serve immediately.