A great lemon bar should have a no-nonsense tart-sweet curd filling above and a flaky-yet-firm short bread crust below. The two together create an experience that approaches religious.
The secret to lemon bars isn’t in the ingredients per se (a top-notch lemon curd filling is defined more by what you leave out of it than what you put into it), it’s in the technique. Too many lemon bar recipes call for a liquid filling to be poured into an unbaked crust. This simplifies the process to be sure, but creates a soggy, paste-like bar. Pre-baking the crust, then pouring on the warm curd while the crust is still hot creates the magic texture combo. You’ll need a candy thermometer to get the process just right. The ingredients are:
8 ounces soft butter
10 ounces (2 cups) all-purpose flour
3.5 ounces (1/2 cup) sugar
a pinch of salt
Lemon curd cooked to 170 degrees F (you’ll need 50% more than the recipe makes, but it scales up very easily)
Powdered sugar for dusting
Preheat your oven to 350 and have all the ingredients for your lemon curd laid out and waiting. Combine the crust ingredients in a bowl or in the bowl of a mixer and stir until a soft dough comes together. Press into a 9″ x 13″ baking dish. Let the crust rest for 10-20 minutes, then bake it for 20 minutes until it is lightly golden.
Meanwhile, prepare the lemon curd. Ideally, what you’d like to do is combine all the ingredients (save for the lemon zest) and start the cooking about five minutes before the crust is due to come out. Once the curd hits 170, take it off the heat. Remove the pan from the oven, stir the zest into the curd and pour it into the crust. Return the pan to the oven for 10-12 minutes, until the curd reaches it’s final temperature, 196 degrees F, and thickens.
Remove the pan from the oven and cool on a wire rack for 45 minutes, then refrigerate at least two hours or overnight. Slice and serve.