1. 1. In a large mixing bowl, cream the butter and sugar together until light and fluffy.

2. 2. Beat in the egg and vanilla extract.

3. 3. In a separate bowl, whisk together the flour, baking powder, and salt.

4. 4. Gradually add the dry ingredients to the wet ingredients, mixing until a dough forms.

5. 5. Divide the dough in half, shape each half into a disk, wrap in plastic wrap, and refrigerate for at least 30 minutes.

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

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

8. 8. Use cookie cutters to cut out shapes, and transfer the cookies to the prepared baking sheets.

9. 9. Bake for 8-10 minutes, or until the edges are lightly golden.

10. 10. Allow the cookies to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.

11. 11. Prepare the buttercream frosting and divide it into two bowls. Color one portion red and the other green.

12. 12. Pipe the colored buttercream onto the cooled cookies and decorate with sprinkles, nonpareils, and other festive toppings.