Put egg yolks in a deep metal pan or metal bowl. Add lemon juice, whisk until frothy.
Place your pot (or bowl) over the pot of boiling water, and continue whisking. Do not let your pot dip into the water, or your yolks will scramble.
Slowly whisk in melted butter, and continue whisking your pot over the steaming water.
Add sea salt to taste, and a healthy sprinkle of cayenne pepper.