This simple fish bake delivers tons of flavor but requires minimal prep. You’ll need a good amount of capers—¼ to ½ cup—along with some caper brine, which brings saltiness and tang to balance the sweetness of the vegetables. The onion and tomatoes get a head start on baking; once they’re soft and jammy, the fish fillets, which have been briefly marinated, are placed on top. If your fillets are thicker or thinner than about 1 inch, adjust the baking time up or down to ensure the fish doesn’t wind up dry and overcooked. Serve with warm, crusty bread or a rice or orzo pilaf.