Preheat the oven to 350 degrees F (175 degrees C). Coat a 9x13-inch baking dish with cooking spray.

Combine 2 cups flour, butter, and 1/2 cup confectioners’ sugar in the bowl of a food processor; pulse until mixture resembles coarse crumbs. Press into the prepared baking dish.

Bake in the preheated oven until crust edges are golden brown, 18 to 22 minutes. Cool to room temperature.

Beat white sugar, eggs, 1/4 cup flour, lemon juice, baking powder, and lemon zest together in a bowl using an electric mixer until light and fluffy; pour onto the cooled crust.

Bake in the oven until custard is set, 25 to 28 minutes. Completely cool lemon squares; dust top with confectioners’ sugar.