1-First Step: Prep your workspace and dry mix Combine 2 cups all-purpose flour plus extra for dusting, 1/2 teaspoon baking powder, and 1/4 teaspoon salt in a medium bowl. Whisk it together, then set it aside. This keeps the dry ingredients evenly distributed so your dough stays consistent.

2-Second Step: Cream butter and sugar until pale and fluffy In a large bowl, beat 12 tablespoons unsalted butter at room temperature with 3/4 cup granulated sugar until pale and fluffy, about 1 to 2 minutes. Add 1 egg at room temperature and mix until combined, then add 1 teaspoon vanilla extract and stir.

3-Third Step: Combine dry and wet gently Add the dry ingredients to the wet ingredients in two parts. Mix gently until just combined. Overmixing can make dough tougher, which affects the swirl look and sliceability.

4-Fourth Step: Divide dough and color the layers Divide the dough into three equal balls. Add 1/2 to 1 teaspoon red food coloring to one ball and 1/2 to 1 teaspoon green food coloring to another, mixing until fully blended. Leave the third ball plain so you have your white layer.

5-Fifth Step: Flatten, wrap, and chill at least 1 hour Flatten each dough ball into a square, wrap in plastic, and refrigerate for at least one hour. This chilling step firms the dough so it rolls without tearing.

6-Sixth Step: Roll each color into a 10-inch square Roll each colored dough between parchment paper to a 10-inch square. Then refrigerate again for 30 minutes.

7-Seventh Step: Layer squares and trim for straight edges Layer the dough squares with red on bottom, white in the middle, and green on top, lining up the edges. Trim the edges with a pizza cutter to make straight, even lines.

8-Eighth Step: Roll into a tight log and chill Carefully roll the layered dough into a log starting from a straight edge. Pinch the seam to seal, wrap in plastic, and chill for one hour until firm.

9-Ninth Step: Preheat and line baking sheets Preheat the oven to 350°F (175°C). Line baking sheets with parchment or a silicone mat.

10-Tenth Step: Slice rounds and space them out Slice the log into 1/4-inch thick rounds and discard the ends. Place cookies about 2 inches apart on the baking sheets.

11-Eleventh Step: Bake, cool, and finish strong Bake for 12 to 15 minutes until the cookies are set. Cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

12-Final Step: Store properly (and keep the swirl looking fresh) Once fully cooled, store in an airtight container at room temperature for up to 4 to 5 days. For longer storage, freeze baked cookies for up to 2 months and thaw at room temperature before serving. Dough logs also freeze well. Wrap tightly and freeze, then thaw in the fridge overnight before slicing.