Step 1

Prepare Salad: Place the balsamic vinegar in a medium mixing bowl. Slowly pour in the olive oil, whisking continuously until a broken emulsion forms. Add the basil, cilantro, and season to taste with salt and pepper. Add the halved tomatoes to the bowl and toss to coat. Allow to marinate as you prepare the fish.

Step 2

Prepare Baked Sea Bass: Preheat oven to 400°F (205°C) with a rack in the center position. Line a half sheet pan with foil and place the fish on top. Rub the skin lightly with olive oil. Rub the inside of the fish with the lemon juice and season on all sides with salt and pepper.

Step 3

Stuff the cavities with the sliced lemon rounds, sliced shallot, and cilantro sprigs. Bake the fish until just opaque in the center roughly 15 minutes to 25, depending on their size. Transfer to platter, spoon the tomato salad around the fish, and serve immediately.