Antoni Porowski's Salty Lemon Squares
- 1 cup all-purpose flour
- 1/4 cup granulated sugar
- 1/2 teaspoon kosher salt
- 8 tablespoons (1 stick) unsalted butter, melted and slightly cooled
- 2 large eggs
- 1 cup granulated sugar
- 1/2 teaspoon baking powder
- Finely grated zest of 1 large or 2 medium lemons (1 1/2 to 2 tablespoons)
- 1/4 cup fresh lemon juice (from 1 large or 2 medium lemons)
- Confectioners' sugar for dusting
- Flaky sea salt, such as Maldon, for sprinkling
Heat the oven to 350 degrees, with a rack in the middle. Line an 8-inch square baking pan with two sheets of foil, shiny side up, crisscrossing them to leave an overhang on all sides. Lightly spray with nonstick cooking spray or grease with butter.
For the crust:
- In a large bowl, whisk together the flour, sugar, and salt. Add the cooled melted butter and stir to combine. Turn the mixture out into the baking pan and press evenly over the bottom. Bake until the edges are just beginning to brown, 18 to 22 minutes.
For the filling:
- With an electric mixer, beat the eggs in a medium bowl until combined. Add the granulated sugar, baking powder, lemon zest, and lemon juice and beat on medium-high until the mixture is frothy, 2 to 3 minutes.
- Pour the filling into the hot crust. Return the pan to the oven and bake until the filling is just set, 22 to 25 minutes. Let cool completely in the pan on a wire rack, at least 1 1/2 hours. For the best flavor and easiest cutting, chill in the refrigerator at least 4 hours, or up to 1 day. (The bars can be covered and refrigerated for up to 3 days or frozen for up to 1 month. Thaw, unwrapped, for 1 hour at room temperature before serving.)
- To serve, cut the bars into 2-inch squares, then dust with confectioners' sugar and sprinkle with flaky salt.
Tip: After grating the lemons, warm them in the microwave for 5- to 10-second intervals until just a bit warm, 15 to 30 seconds, which will help release the most juice. The flavor of these bars deepens overnight, so make them a day ahead if you can.