6 egg yolks
3/4 cup granulated sugar
2/3 cup fresh lemon juice
1/2 cup cold butter, cut into 1/2-inch pieces
1 tbsp lemon zest
Whisk the egg yolks and strain through a fine mesh sieve. Whisk the egg yolks and sugar together in a medium saucepan. Stir in the lemon juice and cook over medium-low heat, stirring constantly with wooden spoon. Do not allow it to come to a boil. Cook until the mixture coats the back of a spoon. Remove from the heat and whisk in the butter and lemon zest. Transfer to a bowl and cover with plastic wrap or pour into sealed jars and refrigerate for up to 3 weeks. Makes 2 cups.
Source: Wanda's Pie in the Sky, 2002