**Mix the dry ingredients**
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
**Cream the butter and sugar**
In a large mixing bowl, use an electric mixer to beat the softened butter and granulated sugar until light and fluffy, about 2–3 minutes.
**Add the wet ingredients**
Mix in the egg and vanilla extract until well combined.
**Combine the wet and dry ingredients**
Gradually add the dry ingredients to the wet ingredients, mixing just until the dough comes together.
**Divide and color the dough**
Divide the dough into two equal portions. Leave one portion plain. Add a few drops of pink or red gel food coloring to the other portion and mix until the color is evenly distributed.
**Roll out the dough**
Roll each portion of dough between two sheets of parchment paper into a 1/4-inch thick rectangle. Try to make the rectangles the same size.
**Layer and roll**
Peel off the top layer of parchment paper from both doughs. Place the colored dough on top of the plain dough, aligning the edges as closely as possible. Gently press them together with a rolling pin. Starting from one long edge, tightly roll the dough into a log.
**Chill the dough**
Wrap the dough log in plastic wrap and refrigerate for at least 1 hour, or until firm.
**Slice and bake**
Preheat your oven to 350°F (175°C). Line baking sheets with parchment paper. Slice the chilled dough log into 1/4-inch thick rounds. Place the cookies on the prepared baking sheets, about 2 inches apart.
**Add sprinkles (optional)**
If using sprinkles, gently press them onto the tops or edges of the cookies before baking.
**Bake**
Bake for 10–12 minutes, or until the edges are just set. The cookies should not brown.
**Cool and serve**
Allow the cookies to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.