Preheat oven to 350℉. Butter a 13"x9"x2" pan. Set aside.

In a food processor, combine 2 cups of flour, butter, 1/2 cup confectioners' sugar, and coconut. Process in bursts until a moist dough ball forms. Press the dough into the bottom of the prepared pan and smooth until even. Bake for 20 minutes, until the edges are golden and the middle is set.

Meanwhile, in a large bowl, whisk together 2 cups sugar, eggs, lemon juice, baking powder, and remaining 1/4 cup flour. Whisk until well blended. When the crust is done in the oven, remove the pan and pour the lemon batter over the top of the hot crust. Return to the oven and bake for another 25 minutes, until the edges are lightly browned and the middle is set.

Remove from the oven and cool on a rack. Cut into squares and dust with extra confectioners' sugar.