01 - Whisk together flour, baking powder, and salt in a medium bowl. Set aside for later use.
02 - Beat butter and sugar in a large bowl until light and fluffy. Add egg and vanilla, mixing until fully combined.
03 - Gradually incorporate flour mixture into wet ingredients, mixing just until dough forms. Avoid overmixing.
04 - Separate dough into three equal portions for coloring.
05 - Mix one dough portion with cocoa powder until completely incorporated and color is uniform.
06 - Blend second dough portion with strawberry powder. Add pink food coloring drop by drop if deeper color desired.
07 - Keep third portion plain for vanilla layer.
08 - Roll each dough portion between parchment sheets into 10x6-inch rectangles. Chill for 20-30 minutes until firm.
09 - Layer dough sheets: chocolate on bottom, vanilla in middle, strawberry on top. Press gently to adhere.
10 - Roll stacked dough tightly from long edge into a log. Wrap in plastic and chill for at least 1 hour until very firm.
11 - Preheat oven to 350°F. Line baking sheets with parchment paper.
12 - Cut chilled log into 1/4-inch rounds. Arrange 2 inches apart on prepared baking sheets.
13 - Bake for 10-12 minutes until edges are lightly golden. Cool on sheets for 5 minutes, then transfer to wire rack.