If fish fillets are large, cut into pieces. Mix butter and lemon juice. In another bowl, mix flour, salt, and white pepper. Dip fish into butter mixture, coat fish with flour mixture. Place fish in ungreased square baking dish. Pour remaining butter mixture over fish, sprinkle with paprika. Cook uncovered in 350 oven until fish flakes easily with a fork, 25-30 min. Garnish with parsley sprigs and lemon slices if desired.