In a large bowl, beat together butter and sugar. Stir in Key Lime zest and juice.
In a separate bowl, stir flour, baking powder, and salt until well combined. Stir in pecans. Fold dry mixture into butter mixture and beat until combined. Bring the mixture together with your hands and form into two logs. Refrigerate for 30 minutes.
Preheat oven to 350 degrées. Line a baking sheet with parchment paper.
Cut into ¼ inch thick rounds and place on the prepared baking sheet. Bake for 10 to 12 minutes, until lightly browned. (Make sure you leave ample space between the cookies because they will spread.
Allow to cool for 10 minutes on the baking sheet and then transfer to a baking rack. Dust with confectioners sugar and allow to cool on the rack.
Note: Like most gluten free goodies, these are best the day they are made. If you are making them in advance I recommend freezing. I love to crisp them back up in the oven!