These fragrant and delicately flavored lemon bars are specially designed for bake sales, where a semifirm texture and compact package come in handy for the buy-on-the-fly crowd. The contrast between the confectioners' sugar topping and the bright lemon-yellow filling is gorgeous. Don't cut them too large: just a few bites satisfy nicely.
Yields 24 bars
Prepare the Quick Cookie Bar Crust and allow it to cool in the pan.
Heat the oven to 350° F. Combine the sugar, flour, salt, eggs, and yolk in a large mixing bowl. Whisk until smooth. Whisk in the melted butter, then the milk. Stir in the lemon juice, lemon zest, and vanilla extract until evenly blended.
Pour the filling over the crust and tilt the pan gently from side to side to spread it evenly. Bake the bars on the center oven rack until the filling is set and just barely beginning to turn golden, 22 to 25 minutes; do not overbake.
Transfer the pan to a wire rack to cool. When the bars are barely warm, dust them lightly with confectioners' sugar using a sifter or fine sieve. Chill for at least 1 hour, then lightly dust them again with confectioners' sugar before slicing.