From the Ball recipe file http://www.freshpreserving.com…..?recipe=15

Lemon CurdMakes enough for 1 9-inch tart

You will need:
 6 large egg yolks
 3/4 cup sugar
 Grated peel of one large lemon
 1 cup fresh lemon juice (about 5 medium)
 1/2 cup (1/4 lb) cold unsalted butter, cut into 8 pieces
 1 Plastic Ball® (16 oz) Freezer Jars

Directions:
1.) PRESS egg yolks through a sieve set over a heavy saucepan to remove all egg whites.
2.) ADD sugar, lemon peel and lemon juice. Whisk just to combine.
3.) COOK over medium heat, stirring constantly with a wooden spoon. Make sure to stir down the sides of the saucepan. Cook until mixture coats the back of the wooden spoon, about 20 minutes. Remove from heat.
4.) ADD butter, one piece at a time, stirring after each addition to assure the mixture is smooth.
5.) LADLE lemon curd into clean jars to fill line. Chill until set, about 1 hour. Twist on lids. Label.
6.) FREEZE up to 1 year.