1 partially baked 9-inch Great Unshrinkable Tart Shell, or your favorite sweet tart shell
1 average-sized lemon (about 4 1/2 ounces; 130 grams), rinsed and dried*
1 1/2 cups (300 grams) sugar
1 stick (4 ounces or 115 grams) unsalted butter, cut into chunks
4 large eggs
2 tablespoons (14 grams) cornstarch
1/4 teaspoon table salt
Center a rack in the oven and preheat the oven 350°F (165´C). Place the tart shell on a baking sheet, which you can line with foil or parchment paper to make any spills a breeze to clean up.
Slice the lemon into thin wheels, remove any seeds, and toss the rounds — lemon flesh and peel — sugar and chunks of butter into the container of a food processor. Process, scraping down the sides of the container as needed, until the lemon is thoroughly pureed. Add the eggs, cornstarch and salt and pulse until the batter is smooth.
Pour into prepared tart shell. It will fill it completely but if due to slight variances in tart pans, egg sizes, lemon sizes or crust thickness, you have too much, do not pour it past the top of of your crust or it will become difficult to unmold later.
Bake 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 it starts to get very light brown on top.
Let cool on rack, unmold tart pan and serve. I actually prefer this tart completely chilled, which makes it a great dessert to make in advance of a dinner or party.
* Meyer lemons are the first choice here. They’re milder with thinner skin. But if you know that you do not mind a stronger lemon and rind kick, feel free to use a regular lemon, which will have a stronger flavor and a higher proportion of skin to flesh. If your lemon is not 4 1/2 ounces (Meyers often weigh in closer to 4 ounces) go ahead and cut a wedge out of a second one to keep the lemon flavor in balance with the sweetness of the tart.