For the crust: Preheat the oven to 350 degrees F.
Prepare an 8 inch tart pan by spraying with baking spray. Set aside.
Cream the butter and sugar in the bowl of an electric mixer until light and fluffy. Combine the flour and salt. With the mixer on low, add the dry ingredients to the butter until just mixed. Gather the dough into a ball and press it into the sprayed tart pan. Chill for 10 minutes.
Bake the crust for 15 minutes, until very lightly browned. Let cool on a wire rack. Do not prepare the filling until the crust has chilled. The lemon juice will begin to "cook" the eggs and the filling will be rubbery after baking.
For the filling: Whisk together the beaten eggs, sugar, lemon zest, lemon juice, and flour. Pour over the chilled crust. Place the tart pan on a cookie sheet to catch any drips. Bake at 350 degrees for 30 minutes, until the filling is just set. Let cool to room temperature then chill before slicing. If you have a 2-piece tart pan, remove the outer ring after cooling. You might have to work a knife around the edge before removing the ring.
Slice with a very sharp knife and dust with confectioners' sugar and garnish with whipped cream just before serving.