Mix or whisk egg yolk, egg, and sugar in heavy bottomed saucepan until light and pale.
Add lemon juice and zest
Stirring constantly, cook over medium heat until thick and bubbling, about 5-7 minutes
It should be thick enough to coat the back of a spoon
Remove from heat and stir in butter one tablespoon at a time
While still warm, strain through a mesh sieve
Let cool and then cover and refrigerate until ready to use. It will thicken as it cools.
Notes
Try to only zest the yellow parts of the lemon. The white part can be bitter.
Make sure to continuously stir the lemon curd mix as it cooks. The constant stirring helps ensure the egg whites don’t separate and cook.
Straining out the lemon zest is optional. I personally prefer a perfectly smooth curd, so I like to strain it, but you don’t mind the zest you can skip this step.
This recipe makes about 1 cup of lemon curd and can be doubled or tripled as needed.
This recipe will last up to two weeks in the fridge or up to 3 months in the freezer.