Easter Lemon Curd Tarts

Zest of 4 lemons
1 1/3 cups granulated sugar
1 1/8 cups lemon juice
6 eggs
1 pound butter, softened
1 package prepared tart shells

Whisk first four ingredients together over double boiler until thick. Strain and then add butter and stir. Chill, and then fill tart shells. Garnish with fruit and or whipped cream.