Whisk the egg yolks and 1 tablespoon of the lemon juice together in a small heavy saucepan or the top of a double boiler. Add a pinch of salt and whisk until the sauce is thick and creamy.
Set the pan over very low heat, or over simmering water in a double boiler, and begin whisking immediately. Continue to whisk until the egg mixture just begins to thicken: Th