Chopped fresh herbssuch as parsley, dill, or thyme, for serving
Place a rack in the center of the oven and preheat oven to 375 degrees F. Lightly coat a 9x13 or similarly sized baking dish with nonstick spray.
Pat the cod dry. Arrange in the baking dish, and season with ½ teaspoon salt and black pepper. Squeeze the lemon over the top.
Heat a large skillet over medium heat. Add the olive oil. Once the oil is hot, add the onion, fennel, tomatoes, and remaining 1/4 teaspoon salt. Saute for 8 to 10 minutes until the onions and fennel are tender and the tomatoes begin to break down. Add the white wine. Let the wine reduce for 1 minute, then add the capers and red pepper flakes.
Spoon the tomato-fennel mixture around the cod. Place in the oven and bake 12 to 15 minutes, until fish is opaque and flakes easily with a fork. Sprinkle with fresh herbs. Serve hot.
TO STORE: Place leftovers in an airtight container in the refrigerator for up to 2 days. I prefer to store the cod and vegetables separately for easy reheating.
TO REHEAT: To avoid drying out the fish, rewarm it in a baking dish in the oven at 350 degrees F until heated through. Add a squeeze of fresh lemon juice to wake the flavors back up. You can also reheat this dish very gently in the microwave or in a skillet on the stove. The vegetables can be warmed in the oven, on the stove, or in the microwave.