In a small sauce pan, combine the peppercorns, salt, and vinegar and reduce until it is almost dry. Remove from the heat and add the water. Transfer to a bain-marie or a clean stainless-steel or glass bowl on top of a pot of lightly simmering water. The bowl should not touch the water.
Add the egg yolk and beat with a whisk until they have become thick and creamy - reaching the sabayon stage - leaving behind ribbons when the whisk is lifted out of the egg yolks.
Remove the bowl from the heat and use a ladle to slowly beat in the warm clarified butter - adding it little by little until the sauce begins to thicken and take form. Then your stream can be increased to a steady thin stream. If the sauce starts to get too cold, return it over the heat briefly or whisk in a few drops of hot water.
Beat in the lemon juice to taste and adjust for seasoning with the salt and cayenne.
*Note: When working with raw eggs, remember that there is always risk of food-borne illness. Consult a doctor right away if you begin to feel sick.