Combine egg yolks, whole eggs, and granulated sugar in a medium saucepan, whisking until smooth for about 1-2 minutes.

Gradually whisk in fresh lemon juice and zest along with a pinch of salt until thorough.

Cook the mixture over low to medium heat, stirring constantly for 8-12 minutes until thickened.

Remove from heat and strain through a fine-mesh strainer into a bowl to ensure smoothness.

While warm, stir in small cubes of unsalted butter until completely melted and incorporated.

Press plastic wrap directly onto the surface of the curd and cool to room temperature before refrigerating.

Store in an airtight container in the refrigerator for up to ten days or freeze for longer storage.