Heat the olive oil in a large, covered skillet over medium-high heat until it is almost smoking. Pat the fish fillets dry and season with salt and pepper. Sear the fish, without jostling, for 2 to 3 minutes, or until a nice brown crust forms. Flip fillets and brown the other side, for about 2 to 3 minutes. Remove the bass onto a plate and keep warm while preparing the sauce.

Once the sauce is ready, return the fish fillets to the pan with the sauce. Cover and braise gently over low heat until the fish is tender and opaque throughout about 3 to 5 minutes. Place fish pieces on a dish or serving tray, spoon sauce over, and add parsley, tomatoes, and browned pieces of pancetta or bacon before serving.