01 - In a medium mixing bowl, whisk together the flour, baking powder, baking soda, and salt until evenly blended.
02 - Using an electric mixer, beat unsalted butter and granulated sugar in a large bowl on medium speed until light and fluffy, about 2 minutes.
03 - Beat in eggs one at a time, mixing thoroughly after each addition. Stir in vanilla extract, key lime zest, and key lime juice until the mixture is fully incorporated.
04 - Gradually add the prepared dry ingredients to the wet mixture, mixing on low speed until just combined. Do not overmix.
05 - Fold in sweetened shredded coconut by hand until evenly distributed throughout the dough.
06 - Cover the bowl and refrigerate the dough for at least 30 minutes to firm up.
07 - Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
08 - Scoop tablespoon-sized portions of dough and roll each into a ball. Coat each ball generously in powdered sugar.
09 - Arrange dough balls 2 inches apart on prepared baking sheets. Bake for 10 to 12 minutes, or until the edges are set and surfaces display a crinkled pattern.
10 - Let cookies cool on baking sheets for 5 minutes, then transfer to a wire rack to cool completely before serving.