In a shallow bowl, whisk together the flour, Herbes de Provence, salt and pepper. Dredge the fish in the flour, tapping off excess flour.
Heat the olive oil in a large non-stick skillet over medium heat. Working in batches, cook the fish for about 2 minutes per side, until the fish is golden brown. Add more olive oil if necessary if the pan dries up. Transfer the fish to a platter and repeat until all the fillets are cooked.
Lower the heat to medium-low. Stir in the lemon juice, capers and caper juice to the pan. Let the sauce bubble, then whisk in the butter (or more olive oil). Pour the sauce over the fish and garnish with parsley. Serve immediately.