In summer I want a dish that tampers with the tomato-fish formula as little as possible. So instead of cooking the tomatoes, I marinate them, and instead of braising the fish, I grill or roast it. Neither fish nor tomatoes need much help.
Meanwhile, using a sharp knife, make three or four diagonal, parallel slashes on each side of fish, just about down to the bone. Sprinkle inside of fish with salt and pepper, then stuff with remaining garlic, a layer of lemon slices and thyme sprigs. Rub outside of fish with remaining 2 tablespoons oil and sprinkle with salt and pepper.
03To roast, put fish in roasting pan and cook for about 20 minutes (cooking time will depend on fish size). If grilling, cook until firm enough to turn, 5 to 8 minutes. Turn and cook second side for 5 to 8 minutes. Whether roasting or grilling, fish is done when exterior is crisp and a thin-bladed knife passes easily through the flesh.
04Taste tomato mixture and adjust seasoning, adding more oil if needed. Serve fish topped with tomatoes and their liquid.