1.Preheat oven to 350°F.
2.In a large bowl, cream butter and sugar until fluffy. Add egg and egg yolk, beating until creamy. Beat in lime juice and zest just until combined.
3.Stir in flour, baking powder, and salt; mix well. Refrigerate dough 60 minutes, until firm.
4.Shape dough into 1-inch balls and place 1 inch apart on cookie sheets.
5.Bake 10 to 12 minutes, or until light golden. Transfer to wire rack. While still warm, pour confectioners’ sugar into a hand strainer over cookies, and dust cookies lightly.