Preheat oven to 350°F and line baking sheets with parchment paper.
In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
In a large bowl, beat butter and granulated sugar until light and fluffy, about 3 minutes. Add egg, lemon juice, lemon zest, and vanilla, beating until well combined.
Gradually add the flour mixture to the wet ingredients, mixing until just combined. The dough will be slightly sticky.
Place powdered sugar in a shallow bowl. Scoop dough by rounded tablespoons and roll into balls. Roll each ball generously in powdered sugar until completely coated.
Place cookies on prepared baking sheets, spacing 2 inches apart. Bake for 10-12 minutes until edges are set and cookies have crackled. The centers will look slightly underdone. Cool on baking sheet for 5 minutes, then transfer to a wire rack.