Stir together the flour and confectioners’ sugar in a medium size bowl.
Using a stand mixer (or hand held mixer), beat together the butter cubes and the flour and confectioners’ sugar mixture until well combined (but do not overmix to ensure a tender crust)
Press the mixture into an ungreased 9-inch square pan. The crust will be very thin, but make sure to spread it all the way to the edges. (You could also press the crust into an 8-inch square pan to have a slightly thicker crust. I will probably do that next time I make this recipe.)
Bake the crust for 15-20 minutes, or until it’s light brown.
To make the topping
Whisk together the eggs, granulated sugar, lemon juice, flour, and a pinch of salt.
When the crust has finished baking and still hot, pour the topping over it.
Return the pan to the oven, and bake for 20-25 minutes, until the lemon topping appears set (or nearly so). Check the make sure the edges don’t burn.
Remove the bars from the oven, and cool them on a rack. When cool, sprinkle the top of the bars with confectioners’ sugar and serve.
Note: Leftovers can be stored in the refrigerator for up to three days. Do not sprinkle the confectioners’ sugar on the bars if you won’t be eating them immediately.