Preheat your oven to 350°F (180°C). Line a baking sheet with parchment paper.
In a large bowl, cream together the butter and sugar until light and fluffy. Add the egg and vanilla extract; beat until smooth.
1 cup unsalted butter, 1 ¼ cups granulated sugar, 1 large egg, 1 teaspoon vanilla extract
Mix in the flour, baking soda, baking powder, and salt until a dough forms. (If the dough feels crumbly, add 1 tablespoon of melted butter to bring it together.)
2 ¼ cups all-purpose flour, ½ teaspoon baking soda, ½ teaspoon baking powder, ¼ teaspoon salt
Divide the dough into 3 equal parts: Leave one portion plain, tint one with red food coloring, tint the last with blue food coloring. Mix each until fully colored.
Blue food coloring, Red food coloring
Take a small piece from each color and gently roll them together into a ball, creating a swirl or tie-dye effect. Roll each ball in granulated sugar and place on the prepared baking sheet.
Bake for 12–15 minutes, or until the edges are lightly golden and the centers are still soft. Let cookies cool on the baking sheet for a few minutes, then transfer to a wire rack to cool completely.
Enjoy your red, white, and blue treat!