In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

In a large bowl, cream together the softened butter and sugar until light and fluffy, about 2-3 minutes.

Beat in the egg and vanilla extract until fully combined.

Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined.

Divide the dough into 4 equal portions. Add a different gel food coloring to each portion and knead until the color is evenly distributed.

Roll each colored dough portion to about 0.25-inch thickness on a lightly floured surface.

Use alphabet cookie cutters to cut out letters. Transfer to a parchment-lined baking sheet, spacing them about 1 inch apart.

Bake at 350°F (175°C) for 10-12 minutes, or until the edges are lightly golden.

Let cookies cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.

Decorate with edible glitter or sprinkles if desired, once cookies are completely cool.