Create vibrant Tie-Dye Sugar Cookies with a simple swirl technique. Bright, marbled colors baked into buttery sugar cookie dough make these cookies as fun to bake as they are to eat. Perfect for parties, gifts, or just because!
In a large bowl, beat powdered sugar, butter, vanilla, and egg with an electric mixer on medium speed until well blended. Stir in flour, baking soda, and cream of tartar. Divide the dough in half and set one half aside.
Divide the other half of the dough into five portions and place each portion in a separate small bowl. Add food color gel to each bowl, mixing just enough to create streaks of color in the dough.
Place the plain half of the dough onto a lightly floured 12x16-inch sheet of parchment paper. Roll it into a 9x12-inch rectangle. Randomly drop tablespoons of the colored dough over the rectangle. Lightly press and flatten the colored dough into the plain dough with a rolling pin. Using the parchment paper to help, tightly roll the dough from the long side into a log about 12 inches long and 2 ½ inches wide.
Place nonpareils in a rimmed cookie sheet. Transfer the dough roll to the pan and press and roll it in the nonpareils to coat evenly on all sides. Wrap the roll tightly in parchment paper and chill for 2 hours or until firm.
Preheat oven to 375°F. Unwrap the dough, trim off the ends, and discard them. Cut the dough into ¼-inch slices and place them 2 inches apart on parchment paper-lined cookie sheets.
Bake for 7-9 minutes or until the edges are light golden brown. Let rest on cookie sheets for 2 minutes before transferring to a wire rack to cool completely.