Season the fish filets with salt and pepper, then lightly flour. In a skillet, heat the oil and 2 tablespoons of butter. Saute the fish until fully cooked. Set aside.
Saute the banana pieces very lightly (just until they have some color). Place a banana half atop each filet.
Saute the red bell pepper and tomato, then add the remaining 1/2 pound of butter. Let cook until the butter has a hazelnut color, then add the parsley and the juice from the 2 lemons.
Pour the butter mixture over the fish filets. Garnish with lemon slices.