1-First Step: Set Up Your Double Boiler Fill the bottom of a double boiler with 1 to 2 inches of water and bring it to a simmer over medium heat. The water should be gently bubbling, not boiling hard. This setup gives the curd indirect heat, which helps prevent the eggs from scrambling. If you do not own a double boiler, you can place a heatproof bowl over a saucepan, making sure the bowl does not touch the water. Keep your tools ready before you start, since this recipe moves quickly once the heat is on.

2-Second Step: Whisk the Base Together In the top pot of the double boiler, whisk together the egg yolks, granulated sugar, lemon zest, lemon juice, and salt. Keep whisking until the sugar starts to dissolve and the mixture looks smoother. At this stage, the mixture may seem thin, but that is perfectly normal. Use steady motion and make sure the ingredients are fully blended. The lemon zest should be distributed evenly so every spoonful gets that bright citrus scent. Fresh-squeezed juice makes a big difference here, so do not be tempted by bottled juice if you can help it.

3-Third Step: Cook Slowly Until Thickened Continue whisking constantly over the simmering water for about 10 minutes, or until the mixture thickens to a hollandaise-like texture. It should coat the back of a spoon and look glossy. If you want to test it, run your finger across the back of the spoon; if the line stays clear, the curd is ready. Temperature matters here. Low and steady heat is your friend, because high heat can curdle the eggs. This is where patience pays off. The curd should thicken gradually instead of all at once.

4-Fourth Step: Add the Butter Remove the pot from the heat once the curd has thickened. Add the butter pieces one at a time or a few at a time, whisking until each piece melts before adding more. The butter gives the curd its smooth, luscious finish and helps it set up nicely as it cools. If you see a few tiny lumps at first, keep whisking. They usually melt in with the residual heat. The finished mixture should look creamy, shiny, and soft.

5-Fifth Step: Strain If Needed If you want an extra-silky lemon curd recipe, pour the mixture through a fine mesh sieve into a clean bowl or jar. This removes any bits of zest or cooked egg that might have formed. Straining is optional, but it is a great move if you want that bakery-style smoothness. Use a non-reactive bowl or container for the best flavor. Avoid metal equipment when possible, since metal can sometimes give citrus curd a metallic taste.

6-Final Step: Cover, Chill, and Serve Pour the curd into a jar or bowl. Press plastic wrap directly onto the surface to stop a skin from forming, then refrigerate until fully chilled and thickened. The total time is about 1 hour and 15 minutes, including cooling. Once cold, it will be thicker and easier to spread. Serve it on toast, spoon it over yogurt, layer it into cakes, or pair it with scones. If you are already planning a brunch spread, it can be lovely next to something sweet like maple gingerbread coffee cake. That little contrast of cozy spice and bright citrus is downright charming.