Preheat oven to 300 degrees.
In a large bowl, cream together butter and confectioners sugar; then blend in flour and salt.
Press mixture down in a flat buttered cookie pan.
Bake at 300 for 20 minutes.
While crust is baking, in a medium bowl blend together eggs, granulated sugar, lemon juice and rind and pour over crust.
Raise temperature to 350 and bake for an additional 15-20 minutes.
Remove from oven and let cool.
When cooled, sprinkle with additional confectioners sugar and cut into rectangles.