Butter the bottom of a baking dish large enough to accommodate all the fillets in a single row. Rub the fillets, top and bottom, with the olive oil. Place the fillets, skin side down, in the baking dish. Salt and pepper the fillets lightly.
In a small bowl combine the butter, cayenne and lemon juice. Cut this mixture into thin bits and place on top of the fillets. Under a broiler preheated to 500°F place the fish near the top of the oven and broil without turning until the fillets take on a rich, dark color. Reduce the heat to 350°F and continue cooking for a total of 10 minutes. Remove the fish and keep warm. Reserve pan drippings to add to the hollandaise.
For the hollandaise, melt the butter, without allowing it to brown, and remove it to a small pouring bowl.
Stir the egg yolks and water together and whisk the mixture in a bain marie or double boiler over low heat until the mixture begins to thicken. Remove from the heat and allow the mixture to continue thickening as you whisk. Slowly pour the butter into the egg mixture, whisking as you go to allow the butter and egg to blend into an emulsion. Slowly add the lemon juice and the pan drippings from the fish and continue whisking, returning to the heat as needed to keep the mixture warm. Serve immediately.
Top each fillet with a dollop of hollandaise and sprinkle the parsley around.