Zest all of the lemons! You only need 1/2 tsp for recipe, but the zest is so good, you should keep it. One idea is to mix it with a jar of sugar to add to a glass of sweet tea.
Juice all lemons - this should give you around 2/3 cups lemon juice. Make sure to remove the seeds.
In a double boiler, add about an inch or so of water to the bottom, and set on a medium-heat burner. In the top of the boiler, whisk together the cup of sugar and egg yolks until smooth. Then mix in the lemon juice and zest.
When completely smooth, place top of boiler onto bottom and stir constantly about ten minutes. (I use a rubber spatula.) When curd is thicker, begin adding chuncks of butter until melted. Once all of the butter has been melted into curd, remove from heat and pour into your sterilized jars.
Cover tightly with lids. When jars have cooled, I suggest that you place them in the refrigerator. Lemon curd will last about a month or so, not terribly long. I doubt it will stay in your refrigerator that long - it's too delicious!