Prep Lemons: Rinse lemons under running water. For extra cleaning, soak in a water and baking soda solution for 15 minutes.
Zest Lemons: Use a microplane or grater to remove the zest from half the lemon, avoiding discolored spots. For a stronger flavor, zest more of the lemon.
Juice Lemons: Squeeze out the juice from the whole lemon and set it aside.
Double Boiler Setup: Place a heatproof bowl over a pot with simmering water, ensuring the bowl doesn’t touch the water.
Cook Mixture: In the bowl, whisk eggs and sugar until combined. Add lemon zest and juice, stirring continuously until the mixture thickens.
Add Butter: Remove from heat once thickened, add chopped butter, and stir until completely melted and incorporated.
Cover: Use plastic wrap to cover the curd directly, preventing skin formation.
Chill: Let the curd cool at room temperature, then refrigerate while still covered.