Make the lemon curd: Combine the egg yolks, granulated sugar and lemon juice in a medium saucepan over medium heat; cook, whisking, until the mixture begins to thicken, about 8 minutes. Stir in the butter, 1 piece at a time, with a wooden spoon. Cook, stirring, until thick enough to coat the back of the spoon, about 7 more minutes. Strain through a fine-mesh sieve into a medium bowl, pressing the curd through with a rubber spatula. Stir in the lemon zest and salt. Fill a large bowl halfway with ice. Set the bowl of curd on the ice and let cool completely, stirring occasionally.
Make the bars: Coat an 8-inch-square baking dish with cooking spray and line with foil, leaving an overhang on 2 sides. Pulse the cookies in a food processor until finely crushed. Slowly add the melted butter and lemon zest and pulse until the mixture starts coming together.
Transfer the crumb mixture to the prepared baking dish and press firmly into the bottom. Spread the ice cream over the crumb mixture with a rubber spatula; spread the lemon curd on top. Cover with plastic wrap and freeze until firm, about 4 hours or up to 2 days.
Lift out of the pan using the overhanging foil. Cut into pieces and dust with confectioners' sugar.