The best lemon bars are just sweet enough to temper lemon’s acidity while heightening its heady tang. Adding zest to the curd would have detracted from its comforting smoothness with chewy bits. Instead, the wisps of lemon peel bake into the cookie, which is snappier than classic shortbread to provide a contrast to the filling’s softness. Rather than cutting cold butter into flour and powdered sugar for a crumbly bottom as many recipes do, this version combines melted butter with flour and sugar for a sturdy — and simpler — dough. After setting in the oven, the base is covered with the just-as-simple lemon mixture while still hot. Doing so ensures that the layers meld together into a textural ombré so that each bite starts with melt-in-your-mouth curd and ends with a satisfying crispness.

Lemon Bars
Ingredients for the crust:
• Nonstick cooking spray
• 10 tablespoons/140 grams unsalted butter, melted and cooled
• 1/4 cup/50 grams sugar
• 1 teaspoon vanilla extract
• 1 teaspoon fine sea salt
• 2 to 4 lemons
• 1 1/2 cups/200 grams all-purpose flour

Ingredients for the lemon layer:
• 1 1/4 cups/250 grams sugar
• 1/4 cup/33 grams all-purpose flour
• 4 large eggs, room temperature
• Powdered sugar, for dusting
(optional)

Directions:
Prepare the crust: Heat the oven to 350 degrees. Line the bottom and sides of a 9-inch square metal pan with foil. Lightly coat with nonstick cooking spray.

Combine the butter, sugar, vanilla and salt in a large bowl. Finely grate in the zest of 2 lemons (reserving the zested lemons for the lemon layer), then mix until well combined. While stirring, gradually add the flour and stir just until the dough comes together into a mass. Scrape into the prepared pan and gently press the dough into an even layer.

Bake until the center is dry and the edges are golden, 15 to 18 minutes.

While the crust bakes, make the lemon layer: Squeeze 2/3 cup juice from the zested lemons and more fruit if needed. In the same bowl used for the crust, whisk the sugar and flour. Whisk in the eggs until smooth, then whisk in the lemon juice just until incorporated.

When the crust comes out of the oven, whisk the lemon mixture again and then gently pour it over the hot crust. Turn the oven down to 300 degrees.

Bake until the lemon layer is set around the edges and jiggles a tiny bit in the center, about 20 minutes.
Cool completely in the pan, then refrigerate uncovered until cold and fully set, at least 3 hours. Cut into bars and serve cold or at room temperature. The bars can be refrigerated in an airtight container for up to 5 days. If you’d like, dust with powdered sugar right before serving.
Total time: 1 hour, plus 4 hours’ cooling, makes one 9-inch pan (12 to 24 bars).