Lemon-Lavender Bars

Preheat oven to 350 degrees F. Meanwhile, line an 8-inch square baking pan with parchment, leaving a 2-inch overhang. In a food processor, pulse 3/4 cup flour, confectioners' sugar, cornstarch, and 1/2 teaspoon salt to combine. Add butter and lavender, and pulse until the mixture resembles coarse crumbs. Transfer the dough mixture to the prepared pan, cover with plastic wrap, and press the dough evenly into the pan so that it goes up 1/2 inch on the sides. Remove the plastic. Bake dough until set and golden brown, 20 to 25 minutes. Remove from oven and set aside. Reduce oven temperature to 325 degrees F. In a bowl, using an electric mixer on medium speed, beat granulated sugar, eggs, and yolk until pale yellow. Beat in lemon juice and zest, and remaining flour and salt, until well combined. Pour filling over the still-warm crust and bake until filling is set, about 20 minutes. Remove pan from oven and let cool to room temperature; then refrigerate for at least 1 hour. To serve, use the parchment overhang to lift the dessert from the pan. Dust the top with confectioners' sugar and cut into 16 squares.