In a medium saucepan, whisk together sugar and eggs until combined.
Add the lemon juice and zest to the egg mixture, stirring well.
Place the saucepan over medium heat and cook, stirring constantly, until the mixture thickens.
Remove from heat and strain the mixture through a fine-mesh sieve.
Stir in the cubed butter until fully melted and incorporated.
Add a pinch of salt to enhance the flavor.
Transfer the lemon curd to a clean jar and let it cool.
Refrigerate for at least 2 hours to thicken further.
Enjoy your lemon curd on toast or in desserts.