If using salt-packed capers, place them in a small bowl, add cold water to cover and soak for 20 minutes. Drain, rinse well and drain again, then pat dry on paper towels. If using vinegar-packed capers, rinse under cold running water, drain and pat dry.

Mix flour, salt and pepper in a shallow dish. Thoroughly dredge filets in flour.

 In a large nonstick fry pan over medium heat, melt the butter with the olive oil.

Add the fish in the pan and cook, turning once, until browned on both sides and opaque throughout but still moist looking in the center when tested with a knife, 6 to 8 minutes total.

Transfer the fish to a warmed platter and cover loosely with aluminum foil.

Add the shallots and garlic to the pan and cook, stirring often, until fragrant, about 2 minutes. Add the wine and lemon juice, increase the heat to medium-high and boil until the sauce thickens slightly, 2 to 3 minutes. Stir in the parsley, capers and lemon zest, and season with salt and pepper.

Place cooked filets on plates or in shallow bowls, then pour sauce over the filets and serve.