Fresh Lemon-Lime Squares

Preheat the oven to 350°F. Line an 8-inch square baking dish with foil, leaving an overhang of 2 inches on opposite sides. Coat the foil with cooking spray.

In a small bowl, whisk ⅔ cup of the flour, the cornmeal, baking powder, and salt. Using a fork, in a small bowl, beat the eggs and egg white. Transfer 1 tbsp of the beaten eggs to a cup and stir in 1 tsp water. Set aside both egg mixtures.

Using an electric mixer on low speed, in a medium bowl, beat the butter until creamy. Add ¼ cup of the granulated sugar and beat until blended. Beat in the egg-water mixture. Add the flour mixture and beat until blended. Press the dough evenly onto the bottom and ¼ inch up the sides of the prepared baking dish. Bake until golden brown, about 22 minutes.

Meanwhile, in a medium bowl, whisk the remaining ⅓ cup flour and ¾ cup granulated sugar. Whisk in the remaining egg mixture until blended. Whisk in the citrus zests and juices until blended.

Reduce the oven temperature to 300°F. Pour the lemon-lime filling over the hot crust. Bake until the filling is set, 20 to 25 minutes. Let cool in the pan on a wire rack. Refrigerate until the crust and filling are cold, at least 1 hour or up to 8 hours. Dust the top with the powdered sugar. Remove from the pan using the foil overhang. Cut into 16 squares.