I got this recipe years ago out of the Washington Post.  This is hands down, my most requested treat!  This recipe makes 24 – 36 bars (depending on how big you cut them)

You will need:

• 8 oz (2 sticks) unsalted butter, softened, plus additional for greasing your baking dish
• 1/2 cup confectioners (powdered) sugar, plus more for finishing
• 1 teaspoon vanilla extract
• 2 cups flour
• 4 large eggs
• 2 cups sugar
• 1 tablespoon finely grated lemon zest
• 6 tablespoons lemon juice (abt 2 large lemons)

1. Set oven rack on the middle level and preheat oven to 350 degrees.  Lightly grease a 9×13 inch baking dish and line it with over-sized, buttered parchment paper or aluminum foil
2. With an electric mixer on medium speed , beat the butter.  Add the confectioners sugar and vanilla extract and beat until light, 1 to 2 minutes.  Reduce the speed to low and beat in the flour.
3. Pat the dough evenly over the bottom of the prepared baking dish.  Bake for 20-25 minutes or until golden and baked through.
4. While it’s baking, in a large bowl, whisk the eggs just enough to break them up.  Without overmixing, add in the sugar, them the lemon zest and juice
5. As soon as the base is baked, pour the lemon topping over it and return the baking dish to the oven.
6. Bake for 25 to 30 minutes, or until  the topping is set and firm.  Transfer to a wire rack to cool.
7. When completely cooled, remove by lifting the parchment paper or foil and transfer to a work surface.
8. Cut into 2-inch squares.  Just before serving, dust with confectioners sugar.
9. They can be stored in an air-tight container at room temp for several days.