01 - Whisk together flour, baking powder, and salt in a medium bowl until evenly combined. 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 on low speed just until a cohesive dough forms. Be careful not to overmix.
04 - Separate dough into three equal portions for flavoring.
05 - Knead cocoa powder into one dough portion until completely integrated and color is uniform throughout.
06 - Mix freeze-dried strawberry powder into a second dough portion until evenly distributed. Add pink food coloring if desired for more vibrant color.
07 - Leave the remaining dough portion unflavored for the vanilla layer.
08 - Roll each dough portion between two sheets of parchment paper into rectangles measuring approximately 10x6 inches. Refrigerate each sheet for 20-30 minutes until firm.
09 - Layer the chilled dough sheets: place chocolate on the bottom, vanilla in the center, and strawberry on top. Gently press layers together to ensure they adhere.
10 - Roll up the stacked dough starting from the long edge into a tight log. Wrap securely in plastic wrap and refrigerate for at least 1 hour until very firm.
11 - Preheat oven to 350°F. Line baking sheets with parchment paper.
12 - Cut the chilled dough log into 1/4-inch thick rounds. Arrange cookies 2 inches apart on prepared baking sheets.
13 - Bake for 10-12 minutes until edges are just lightly golden. Let cool on baking sheets for 5 minutes before transferring to wire racks to cool completely.