1 large egg yolk 2 tablespoons cold water 1 tablespoon fresh lemon juice Salt to taste 1 pinch cayenne pepper 4 tablespoons cold unsalted butter, cubed Place egg yolk into a large stainless steel bowl. Whisk in water, lemon juice, salt, and cayenne pepper. Add butter cubes. Place bowl over low heat. Whisk continually until butter melts and mixture gets foamy, about 3 minutes. Continue whisking over low heat until sauce is to your desired thickness, 3 to 5 more minutes.