Begin by preparing your dry ingredients. In a medium bowl, whisk together the all-purpose flour, baking powder, and salt until well combined.

In a large mixing bowl, cream together the unsalted butter and granulated sugar until light and fluffy. Add in the large egg and vanilla extract, mixing until fully incorporated.

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

Divide the dough into three equal parts. Dye one part red and the other green, leaving one portion uncolored. Wrap each portion tightly in plastic wrap and refrigerate for at least 45 minutes.

Roll each colored dough into a rectangle, stack them in the order: green, uncolored, and then red. Roll tightly into a log shape.

If desired, roll the cookie log in sprinkles for decoration. Chill again for at least 45 minutes.

Preheat your oven to 350°F (175°C). Slice the cookie log into ½-inch thick rounds and place on parchment-lined baking sheets.

Bake for 13-15 minutes, then allow to cool on the baking sheet before transferring to a wire rack.