Step 1: In a medium bowl, whisk together flour, baking powder, and salt.
Step 2: In a large bowl, cream butter and granulated sugar until light and fluffy.
Step 3: Beat in egg and vanilla extract until well combined.
Step 4: Gradually mix in dry ingredients until a dough forms.
Step 5: Wrap dough in plastic and chill for at least 1 hour.
Step 6: Preheat oven to 350°F (175°C) and line baking sheets with parchment paper.
Step 7: Roll out dough to 1/4-inch thickness and cut into tree shapes using cookie cutters.
Step 8: Press each cookie into sparkling sugar to coat one side.
Step 9: Place cookies on prepared baking sheets and bake for 8-10 minutes until edges are lightly golden.
Step 10: Cool on wire racks and optionally decorate with royal icing.