Serves: 4 servings (75ml)1) Put the egg yolk, lemon juice, and cayenne in a blender. Pulse a couple times to combine.
3) With the blender running, gradually add the melted butter into the egg to make a smooth frothy sauce. If the sauce is very thick, blend in a teaspoon of lukewarm water loosen it up.
4) Season with the salt and serve immediately or keep warm in a small heat-proof bowl set over hot (but not simmering) water until ready to serve.