In a medium saucepan over low heat, whisk together the 4 large egg yolks and 1 cup sugar until the sugar has dissolved.
Whisk in ½ cup fresh lemon juice (about 3–4 lemons), 1 tablespoon fresh lemon zest, and ¼ teaspoon coarse Kosher salt.
Cook over low heat, whisking constantly, until thick enough to coat the back of a spoon (about 8–10 minutes). Do not stop whisking or you run the risk of cooking the eggs into scrambled eggs.
Remove from heat and whisk in the cubed 6 tablespoons unsalted butter a few cubes at a time until glossy and smooth.
Strain through a fine mesh sieve (to catch any egg bits that might remain) into a bowl/jar (optional but recommended).
Press plastic wrap directly on the surface and refrigerate until chilled and thickened. The mixture will not be fully thick when you start to chill it.
If you’ve tried this recipe, come back and let us know how it was in the comments or star ratings.
Notes
Make-Ahead: Lemon curd is a great make-ahead recipe since it needs time to chill and thicken. Prepare it up to 5 days in advance and store it covered in the refrigerator until ready to use.Storage: Store homemade lemon curd in an airtight container or glass jar in the refrigerator. For the smoothest texture, press plastic wrap directly onto the surface before sealing with a lid to prevent a film from forming.Shelf Life: Lemon curd will keep in the refrigerator for up to 1 to 2 weeks when stored properly. For longer storage, freeze it in a freezer-safe container for up to 3 months, then thaw overnight in the refrigerator before using.Freezer Instructions: Let the lemon curd cool completely, then transfer it to a freezer-safe container, leaving a little space at the top for expansion. Press plastic wrap directly onto the surface if desired, then seal tightly and freeze for up to 3 months. Thaw overnight in the refrigerator and give it a good stir before using.