Preheat your oven to 350°F and line two baking sheets with parchment paper.
In the bowl of a stand mixer, cream together the butter, granulated sugar, and key lime zest until light and fluffy, about 5 minutes.
Add in the egg, vanilla extract, and key lime juice. Mix until fully combined.
In a separate bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients and mix just until combined.
Scoop the dough into heaping tablespoons. The dough will be soft and sticky. Drop each scoop into powdered sugar, then gently roll to coat and form into a ball before placing on the prepared baking sheet.
Bake for 10 minutes. Cool on the baking sheet for 2 minutes before transferring to a wire rack. Enjoy!
Notes
Make sure your butter is softened and not cold or melted.
Don’t overbake, you want them to stay soft.
Use fresh key lime juice and zest for the best flavor.