Begin by washing the lemons thoroughly and using a microplane or fine grater to zest your lemons.

Juice the lemons, collecting at least 1/2 cup of juice. Remove any seeds from the juice.

In a medium bowl, whisk the eggs until they are well beaten. Set aside.

In the saucepan, whisk together the sugar, lemon zest, and lemon juice until incorporated. Whisk the eggs into the sugar mixture. Over medium-high heat, whisk continuously until the mixture thickens, about 6-10 minutes. The curd will have a custard-like consistency and coat the back of a spoon. Remove from heat and whisk in pieces of butter until the butter is melted completely.

Strain the lemon curd through a fine-mesh sieve into a clean bowl or jar. Use a rubber spatula to press the curd through the sieve, leaving behind any zest or egg bits.

Press plastic wrap onto the surface of the curd to prevent a skin from forming. Allow the curd to cool at room temperature for about 30 minutes before refrigerating. Refrigerate for at least 2 hours, or until the curd becomes set.

Stored in an airtight container, refrigerate for up to 2 weeks or freeze for 3 months.