Humidity tends to make the sugar melt and turn splotchy, so if you live in a humid climate dust the lemon bars with the confectioners' sugar right before serving. We found that it was important to pour the warm filling over a still-hot crust to ensure that the filling cooked through evenly; you can prepare the filling while the crust bakes.

Adjust oven rack to middle position and heat oven to 350 degrees. Make foil sling for 9-inch square baking pan by folding 2 long sheets of aluminum foil so each is 9 inches wide. Lay sheets of foil in pan perpendicular to each other, with extra foil hanging over edges of pan. Push foil into corners and up sides of pan, smoothing foil flush to pan. Grease foil.

For the crust: Process flour, sugar, and salt in food processor until combined, about 3 seconds. Sprinkle butter over top and pulse until mixture is pale yellow and resembles coarse meal, about 8 pulses. Sprinkle mixture into prepared pan and press firmly into even layer. Bake until crust begins to brown, about 20 minutes, rotating pan halfway through baking. (Crust must still be hot when filling is added.)

For the filling: Meanwhile, whisk eggs and yolks together in medium saucepan. Whisk in granulated sugar until combined, then whisk in lemon zest and juice and salt. Add butter and cook over medium-low heat, stirring constantly, until butter is melted and mixture thickens slightly and registers 170 degrees, about 5 minutes.

Immediately strain mixture through fine-mesh strainer into bowl and stir in cream. Pour warm lemon curd evenly over hot crust. Bake until filling is shiny and opaque and center jiggles slightly when shaken, 10 to 15 minutes, rotating pan halfway through baking.

Let bars cool completely in pan on wire rack, about 2 hours. Using foil overhang, remove bars from pan. Cut into 16 pieces and dust with confectioners' sugar before serving. (Bars can be refrigerated for up to 2 days.)

Cleanly Cutting Bar Cookies