Pour 1-inch of water into a large saucepan; over medium heat, bring to a simmer. Once simmering, reduce the heat to low.
Place egg yolks and 1 teaspoon water in a medium mixing bowl and whisk until mixture lightens in color, approximately 1 to 2 minutes. Add the sugar and whisk for another 30 seconds.
Place the mixture over the simmering water and whisk constantly for 3 to 5 minutes, or until there is a clear line that is drawn in the mixture when you pull your whisk through, or the mixture coats the back of a spoon.
Remove the bowl from over the pan and gradually add the butter, 1 piece at a time, and whisk until all of the butter is incorporated. Place the bowl back over the simmering water occasionally so that it will be warm enough the melt the butter. Add the salt, lemon juice, and cayenne pepper. Serve immediately or hold in a thermos to keep warm.
ALTERNATIVE BLENDER DIRECTIONS - slightly different yolk and butter).
Fill blender with hot water and set aside.
Melt butter (1.25 cups) in saucepan on medium heat until foaming. Remove from heat.
Drain blender and dry well.
Put yolks (2) and lemon juice in blender, cover and blend.
Working quickly with blender running, remove insert on lid and slowly pour hot butter into blender in a thin stream of droplets. Discard the milk solids in the bottom of the pan.
Blend until creamy sauce forms.
Season to taste with salt, pepper and more lemon juice.