Wash fillets in cold water and dry well. Sprinkle with salt and pepper. Flour them lightly as to not sticky. Place the oil (olive oil) and 2 tbsp of the butter in a heavy-bottomed pan and preheat to medium-high heat until the butter melts. Add the fish and cook for about 3 minutes on each side (more or less depending on the size of the fillets). Fish is done when catch brown crust. Turn only once. Remove the fish from the pan and turn off the heat. In the frying pan, add the remaining 1 tbsp butter, lemon juice and capers (together with their liquid). Stir with a wire whisk and pour the sauce over the fish fillets. Serve immediately garnished with optional.