In a mixing bowl, combine flour and sugar. Cut in butter until mixture resembles coarse crumbs. Add egg yolk and cold water, mix until dough forms. Press dough into tart pan.
Bake crust for 15 minutes. Remove from oven and let cool.
In another bowl, whisk together sugar, eggs, lemon juice, and lemon zest. Stir in heavy cream. Pour filling into cooled crust.
Bake for 15-20 minutes, or until filling is set. Let cool before serving.