01 - Whisk together flour, baking powder, and salt in a medium bowl. Set aside for later use.
02 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 2-3 minutes.
03 - Add egg and vanilla extract to the butter mixture. Beat until thoroughly combined.
04 - Gradually mix in dry ingredients until a soft dough forms. Be careful not to overmix.
05 - Divide dough in half, shape into discs, wrap in plastic wrap, and refrigerate for at least 1 hour.
06 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
07 - On a lightly floured surface, roll dough to 1/4-inch thickness. Cut out heart shapes using cookie cutters.
08 - Place cookies 1 inch apart on prepared baking sheets. Bake for 8-10 minutes until edges are just turning golden.
09 - Transfer cookies to wire racks and allow to cool completely before decorating.
10 - Beat powdered sugar, meringue powder, and 3 tablespoons water until stiff peaks form. Adjust consistency with additional water as needed.
11 - Tint royal icing with gel food coloring if desired. Separate into different bowls for multiple colors.
12 - Decorate cooled cookies with royal icing using piping bags. Allow icing to set completely at room temperature before serving or packaging.