1. Cream the butter and granulated sugar in a large bowl until light and fluffy.

2. Beat in the egg, lemon zest, lemon juice, and vanilla extract until fully incorporated.

3. Whisk together the flour, baking powder, and salt in a separate bowl.

4. Gradually mix the dry ingredients into the wet ingredients until a dough forms.

5. Wrap the dough tightly and chill for at least 1 hour.

6. Preheat the oven to 350 F (175 C) and line baking sheets with parchment paper.

7. Roll the chilled dough to about 1/4-inch thickness on a lightly floured surface.

8. Cut out tree shapes and transfer them to the prepared baking sheets.

9. Bake for 8 to 10 minutes, until the edges are just starting to turn light golden.

10. Cool on the baking sheet for 5 minutes, then move to a wire rack to cool completely.

11. Whisk powdered sugar, lemon juice, and milk or water until smooth to make a glaze.

12. Add yellow food coloring if desired and stir until evenly colored.

13. Spread or spoon glaze over fully cooled cookies.

14. Drizzle with white icing and add sparkling sugar while the glaze is still wet.

15. Let cookies sit at room temperature until the icing is completely set.