1. In a sliding bag, pour the flour, salt, and pepper, and place the fish pieces inside. Close and mix without breaking the fillets. Set aside.2. In a skillet, melt half of the butter over medium heat.3. Color the fish fillets for 4 minutes on each side, then add the rest of the butter and let it color slightly.4. Sprinkle with lemon juice and add the zest.5. Let it cook for another 3 minutes over low heat, covered, and serve with rice.