Prepare the Ingredients:
Zest the lemons and then juice them. Ensure you have ½ cup of fresh lemon juice and 1 tablespoon of zest.
Mix the Base:
In a medium saucepan, whisk together the egg yolks, whole eggs, sugar, lemon juice, and lemon zest until smooth.
Cook the Mixture:
Place the saucepan over medium-low heat. Stir continuously with a whisk or silicone spatula, ensuring the mixture doesn't boil, for 8–10 minutes, or until it thickens enough to coat the back of a spoon.
Add Butter:
Remove the saucepan from heat and immediately whisk in the butter cubes, one at a time, until fully incorporated.
Strain the Curd:
Pour the lemon curd through a fine-mesh strainer into a heatproof bowl to remove any cooked egg bits and ensure a silky texture.
Cool and Store:
Allow the lemon curd to cool to room temperature, then transfer it to a jar or airtight container. Refrigerate for at least 2 hours to fully set.