Step 1Heat the oven to 350 degrees. Spray a 12-by-9-inch baking pan with nonstick spray. Mix the flour and powdered sugar in a food processor to blend. Add the butter and pulse until the mixture resembles a coarse meal. Sprinkle the mixture over the prepared baking pan and press the dough evenly over the bottom of the pan. Bake until the crust is golden, about 20 minutes. Transfer the pan to a rack, and cool completely.
Step 1Heat the oven to 350 degrees.
Step 2In a large bowl, whisk the granulated sugar and eggs until blended. Whisk in the lemon juice and lemon zest, then whisk in the flour and baking powder. Fold in the coconut. Transfer the mixture to the cooled crust.
Step 3Bake until the top is golden brown and the filling is just set in the center when the pan is gently shaken, about 40 minutes. Transfer the pan to a rack, and cool completely. Dust the top with powdered sugar. Cut into squares. Transfer the lemon bars to a platter and serve.