Step 1Dry the fish thoroughly and set it aside on paper towels.
Step 2Using a sharp knife or zester, remove the zest from the lemon. Chop together the zest, capers and parsley and place in a small bowl. Stir in 3 tablespoons of the olive oil and a couple of grinds of pepper and set aside. Cut the lemon into wedges and set aside.
Step 3In a large heavy skillet, preferably nonstick, heat the remaining tablespoon of olive oil, the butter and garlic over medium-high heat. Lightly dust the fish with flour, brushing off any excess.
Step 4When the oil-butter mixture is sizzling hot, add the fish, but do not crowd (if necessary, cook the filets in batches). Sprinkle with salt to taste, pepper and red pepper flakes. Remove the garlic from the pan when it is golden brown. Cook the fish over medium-high heat until crisp and golden, 1 1/2 to 2 minutes, and turn with a spatula to brown the other side. Season with salt and pepper. Just before removing from heat, squeeze the juice of 1 lemon wedge over the fish.
Step 5Place the fish on a serving dish, drizzle the caper-parsley topping over the top and garnish with the remaining lemon wedges.