Preheat oven to 350. Lightly grease a 13x9x2 inch baking dish. In a medium bowl, combine 2 cups flour, powdered sugar, and 1/2 teaspoon baking powder. Cut in butter with a pastry blender until mixture resembles coarse crumbs. Press mixture into prepared baking dish. Bake 20 to 25 minutes, or until golden browned.
2Key Lime Filling:
In a medium bowl, combine eggs, sugar, juice, 1/4 cup flour, and 1/2 teaspoon baking powder. Pour over hot crust. Bake 22 to 25 minutes or until lightly browned. Serve warm or chilled.