1-First Step: Set up the double boiler Fill the bottom of a double boiler with 1 to 2 inches of water and bring it to a gentle simmer. You want steam, not a rolling boil. If you do not have a double boiler, a heatproof glass bowl set over a pot works well too. This gentle heat matters because it helps keep the eggs from scrambling. Lemon curd can be a little bossy if the heat gets too high, so a calm simmer is your friend. A double boiler also helps prevent a burnt taste or a metallic note.

2-Second Step: Whisk the base ingredients together Place the 4 large egg yolks, 2/3 cup granulated sugar, 1 tablespoon lemon zest, 1/3 cup fresh lemon juice, and 1/8 teaspoon salt in the top of the double boiler. Whisk everything together right away so the sugar starts dissolving and the mixture looks smooth. Using fresh lemon juice is important here. Bottled juice can taste dull or a bit off, and this recipe really shines when the citrus flavor is fresh and lively. If you want the curd a little thicker, replace 2 egg yolks with 1 whole egg before you begin.

3-Third Step: Cook slowly and keep whisking Set the top of the double boiler over the simmering water. Whisk constantly for about 10 minutes, scraping the sides and bottom often. The mixture will slowly thicken into a texture similar to hollandaise sauce. Do not walk away during this part. Constant whisking is what helps prevent curdling and keeps the texture smooth. If you stop whisking, the eggs can cook unevenly, and nobody wants lemon scrambled eggs in dessert form. The curd is ready when it coats the back of a spoon and looks creamy, glossy, and thick. Quick texture tip: if you drag a finger across the back of the spoon and the line stays put, your lemon curd is ready.

4-Fourth Step: Add the butter Remove the bowl from the heat once the curd has thickened. Add the 6 tablespoons of softened unsalted butter, one piece at a time, whisking until each piece melts before adding the next. This step makes the curd shiny, smooth, and rich. If the butter is softened and cut into six pieces, it melts in nicely and blends without clumps. The mixture should look silky and feel creamy when you finish whisking. This is the moment when the kitchen starts smelling like a lemon dessert dream.

5-Fifth Step: Strain if needed and cool If you want an extra smooth finish, pour the curd through a fine mesh sieve into a clean bowl or jar. This removes any tiny bits of cooked egg zest or uneven texture. It is optional, but many bakers love this extra step for a polished result. Press plastic wrap directly onto the surface of the curd. This stops a skin from forming while it cools. Then let it cool, and refrigerate it to thicken further. The total time for this recipe is about 1 hour and 15 minutes, including cooling.

6-Final Step: Serve and enjoy Once chilled, your Lemon Curd is ready to use. Spoon it into tarts, layer it in cakes, spread it on scones, or swirl it into plain yogurt. It also makes a lovely filling for cookies, cupcakes, and breakfast pastries. For the best result, chill the curd until it is fully set. Homemade lemon curd should be smooth, bright, and easy to spread. If it seems a little loose at first, that is normal. Refrigeration does the final thickening.