Whole Lemon Bars

For the crust
• 1 cup (125 grams) all-purpose flour
• ½ cup (65 grams) sugar
• ¼ teaspoon table salt
• ½ cup (115 grams or 1 stick) unsalted butter, cut into chunks, plus extra for greasing pan

For the filling
• 1 small-to-medium-sized lemon (about 4½ ounces or 130 grams, or about 3 inches long)
• 1½ cups (265 grams) sugar
• ½ cup (115 grams or 1 stick) unsalted butter, cut into chunks
• 4 large eggs
• 2 tablespoons (15 grams) cornstarch
• ¼ teaspoon table salt

Place a rack in middle of the oven and preheat your oven to 350 degrees. Cut two 12- inch lengths of parchment paper, and trim each to fit the bottom of an 8- inch square baking pan. Press the first sheet into the bottom and up the sides of your pan in one direction, then use the second sheet to line the rest of the pan, running it perpendicular to the first sheet. Lightly butter exposed parts of parchment or coat them with a nonstick cooking spray. Set the pan aside.
 
Make the crust. Blend the flour, sugar, and salt together in the work bowl of a food processor. Add the butter and pulse until the mixture is powdery, but if firmly pinched, will hold the pinched shape. Turn the dough crumbs into the prepared baking pan and press the dough evenly across the bottom and about ½ inch up the sides. Prick the dough all over with a fork and bake for 20 minutes, or until lightly browned. Should any parts bubble up, gently prick them again with a fork. Leave the oven on.
 
Make your filling. Cut your lemon in half, and here's where I need us all to be, briefly, quite fussy.

Is the white part of the skin especially thick?
If the widest part of the white is ¼ inch thick or less, continue on to the next step; your lemon is good to go. If any part of it is thicker than ¼ inch, however, I find it safest to remove the skin from half the lemon or the bitterness of the pith can overwhelm the bars. To remove the skin, place half the lemon cut-side-down on the cutting board, and remove the skin and pith from the entire half in downward cuts and discard it. The second half, even if just as thick, can be used as is.

Cut your lemon halves into thin rings and discard any seeds. Toss the lemon rounds – lemon flesh and peel – in the bowl of your food processor, add the sugar, and run the machine until the lemon is thoroughly puréed, about 2 minutes. Add the butter and again run the machine until the mixture is smooth, scraping down the sides of the work bowl as needed. Add the eggs, cornstarch, and salt and pulse the machine in short bursts until the mixture is evenly combined.

Pour the lemon mixture over the crust and bake it for 35 to 40 minutes, or until the filling is set. You can test this by bumping the pan a little; it should only jiggle slightly. In my oven, I find that the point at which the filling is set is also when the lemon bars start to get very light brown on top.

Let the pan cool completely on rack or in the fridge. Gently cut around the outside of the parchment paper to make sure no sides have stuck, then gently use the parchment "sling" to transfer bars from pan to cutting board. Cut into 16 squares.

Cooking Notes: Most recipes for whole lemon desserts recommend Meyer lemons. I actually prefer these with regular old grocery store lemons; with some modifications (described above) should their skins be extra thick, I find that they have the perfect balance of tart and fragrance. Nevertheless, to make these bars with Meyer lemons, use just one (of similar size and weight) and reduce the sugar to 1 cup (200 grams). You can double the recipe and bake it in a 9-by-13- inch pan as well. 

VERDICT:  I don't like these quite as well as my favorite potluck lemon bars, but they are good and they are a damn sight easier.  The very best part--throwing the whole lemon in the food processor.  Followed closely by only having the food processor bowl to wash.  Keep!