Preheat your oven to 350°F (175°C) and prepare baking sheets.
In a bowl, whisk together flour, baking powder, and salt.
In a separate large bowl, cream the softened butter and sugar until light and fluffy.
Add the egg and vanilla extract to the butter-sugar mixture, mixing until well incorporated.
Gradually add the dry ingredients to the wet mixture, mixing until just combined.
Scoop out tablespoon-sized portions of dough and roll them into balls.
Roll each ball in glitter or sanding sugar before placing them on the prepared baking sheets.
Bake in the preheated oven for 8–10 minutes or until the edges are lightly golden.
Allow cookies to cool on the baking sheet for a few minutes before transferring to a wire rack to cool completely.