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 3-4 minutes. Add egg and vanilla extract, mixing until fully incorporated.
03 - Gradually add the flour mixture to the wet ingredients, mixing just until a cohesive dough forms. Avoid overmixing to prevent tough cookies.
04 - Split dough into three equal portions. Mix one portion with cocoa powder for chocolate layer. Combine second portion with strawberry powder and optional pink food coloring. Leave third portion plain for vanilla layer.
05 - Roll each dough portion between two sheets of parchment paper into 10x6-inch rectangles. Refrigerate each sheet for 20-30 minutes until firm to the touch.
06 - Carefully place chocolate layer on bottom, top with vanilla layer, then strawberry layer. Gently press layers together to ensure they adhere.
07 - Starting from the long edge, tightly roll stacked dough into a log. Wrap securely in plastic wrap and refrigerate for at least 1 hour until very firm.
08 - Preheat oven to 350°F. Line baking sheets with parchment paper.
09 - Cut chilled dough log into 1/4-inch rounds. Arrange cookies 2 inches apart on prepared baking sheets. Bake for 10-12 minutes until edges are lightly golden.
10 - Let cookies rest on baking sheet for 5 minutes before transferring to wire rack to cool completely.