Place egg yolks in a small sieve set over a saucepan. Stir the yolk membranes to break, then add the lemon juice as you stir the entire mixture through the sieve.
Add the sugar, lemon peel, and lemon juice and whisk just until combined.
Cook over medium heat stirring constantly with a wooden spoon, making sure to stir down the sides of the pan. Cook until the mixture coats the back of the wooden spoon about 10 minutes give or take.
Remove from heat and add butter one piece at a time, stirring after each addition to assure a smooth texture.
This freezes well.