Preheat the broiler.
Butterfly the trout by splitting each fish through the belly from head to tail. Cut through the bones, but do not sever the fish completely. Open the fish like a book, and using a small sharp knife, trim away the skeleton on both halves. Pull out any pinbones. (This procedure may be done by your fish seller.)
Rub the flesh with the butter and season with the salt and pepper.
Place as many fish on your broiler as it can hold without crowding. Broil 3 to 4 inches from the heat source until the flesh is just cooked through, about 4 minutes. Serve immediately with lemon wedges or the flavored butter of your choice.