Zesting the Lemon - Using a small grater, remove the thin outer zest (the yellow part) from the lemons. Be careful to avoid the pith (the white part under the zest) because it has a bitter taste to it. Set aside.
Juicing the Lemons - Next, cut each lemon in half. Remove the seeds that are on top of each half. Squeeze the juice from each lemon into a bowl. Set aside.
For the Eggs - To a medium size bowl, add the eggs. If possible, remove the small white part by the yolk (this white rope-like strand is called the chalaza; the fresher an egg is, the more prominent the chalaza generally is).
Whisk the eggs and set aside for a moment.
Cooking the Lemon Curd - Fill a double boiler with water and bring it to a boil. To the top pan (of the double boiler) add butter.
To the pan, add the lemon juice, lemon zest and sugar. Whisk the ingredients together.
Then, a little at a time, while continuously whisking, very slowly add the eggs. Whisk the mixture each time after adding a little bit of the egg.
Constantly stir so that the mixture is smooth and the eggs don’t curdle.
After all of the egg is poured in the mixture, continue stirring over the heat until the eggs are fully cooked.
Continue to cook until the mixture thickens to the consistency of yogurt or sour cream.
Pour the lemon curd into clean jars and store them in the refrigerator. It should last for 7 days in the refrigerator.
Serve on toast, scones, over ice cream, on cookies, in tarts, or as a pie filling.