Mix the flour with the salt and place on a large plate. Drop the fish into the flour, one at a
time, and shake well to remove any excess. Melt 3 tablespoons of the butter in a small saucepan and
use to brush the fish liberally all over. Place the fish under a grill preheated to medium and cook
for 5 minutes on each side.
Meanwhile, melt the remaining butter in a saucepan. Pour cold water into a bowl that is large
enough to take the bottom of the saucepan and keep near by.
Heat the butter until it turns a golden brown and begins to smell nutty. Remove from the heat
immediately and immerse the bottom of the saucepan in the cold water, to stop the cooking.
Place the fillets on individual plates, drizzle with the lemon juice and sprinkle with the
parsley and preserved lemon, if using. Pour over the browned butter, garnish with parsley sprigs
and serve immediately with lemon wedges for squeezing over.