Patriotic Pinwheel Cookies

In a medium bowl, whisk together flour, baking powder, and salt. Set aside.
In a large bowl, beat the softened butter and sugar together until light and fluffy.
Add the egg and vanilla extract, mixing until well combined.
Gradually add the dry ingredients to the wet mixture and mix until a soft dough forms.
Divide the dough into three equal portions. Leave one portion uncolored, add red food coloring to one portion, and blue food coloring to the third portion. Mix each until the color is uniform.
Wrap each colored dough in plastic wrap and refrigerate for at least 30 minutes.
On a floured surface, roll each dough portion into rectangles of equal size and thickness.
Stack the dough layers (red, white, blue) and press gently to adhere. Trim edges to form a neat rectangle.
Roll the dough tightly into a log, wrap it in plastic wrap, and refrigerate for at least 1 hour.
Preheat oven to 350°F (175°C). Line baking sheets with parchment paper.
Slice the chilled dough log into 1/4-inch thick cookies and place them on the prepared baking sheets.
Optional: Roll the edges of the dough in patriotic sprinkles before baking.
Bake for 10-12 minutes, or until the edges are set. Cool on the baking sheet for a few minutes before transferring to a wire rack.