Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper.
In a mixing bowl, whisk together the flour, baking powder, and salt. Set aside.
In a separate bowl, use an electric mixer to cream together the softened butter and granulated sugar until light and fluffy, about 3-4 minutes.
Add the egg and vanilla extract to the butter mixture, mixing until well combined.
Gradually incorporate the dry ingredients into the wet mixture, mixing until no flour streaks remain.
Divide the dough in half, wrap in plastic wrap, and refrigerate for at least 30 minutes for easier rolling.
Once chilled, roll out the dough on a floured surface to about ¼ inch thickness. Use cookie cutters to cut out your desired shapes.
Place the cookies onto the prepared baking sheets, spacing them about 1 inch apart. Bake in the preheated oven for 8-10 minutes, or until the edges are golden.
Remove from the oven and let the cookies cool on the baking sheets for 5 minutes before transferring them to a cooling rack to cool completely.
For the royal icing, combine meringue powder and powdered sugar in a large bowl. Gradually add water, mixing until the desired consistency is achieved.
If desired, divide the icing into separate bowls and tint with food coloring.
Fill piping bags (or resealable bags with the corner cut off) with icing and decorate the cooled cookies as desired. Allow the icing to dry completely.