Peel strips of lemon peel, being careful not to get too deep to avoid white pith. Squeeze juice into measuring cup. Add to top pot of double boiler.
Whisk eggs well and add to pot along with butter and sugar.
Cook slowly over gentle heat, stirring often, until well combined and thickened. Do not boil.
Alternatively, you can slowly heat in short bursts on low heat in microwave, stirring between sessions. Or heat carefully in regular pot over very low burner using a simmer plate.
Remove rind, allow to cool and refrigerate in covered glass bowl. Will store for a few weeks.
Notes
Nutritional information is based on fresh squeezed lemon juice, salted butter, large eggs and serving size of 1/4 cup.