Preheat the oven to 350 °F. Line a large baking sheet with parchment paper or a silicone mat.

Cream together the butter and sugar on medium speed until light and fluffy. Add the eggs and vanilla, mixing until well incorporated.

In a separate bowl, whisk together the flour, baking soda, cream of tartar, and salt. Beyond Frosting+14Scribd+14Beyond Frosting+14

Gradually blend the dry ingredients into the butter-sugar mixture on medium-low speed until the dough starts to form. Stir in rainbow sprinkles.

Divide the dough into four equal portions. Leave one portion uncolored, and color the other three with gel food colors—pink, royal blue, and violet.

Gently combine the four dough balls in one bowl to create a tie‑dye effect—avoid overmixing to preserve distinct swirls.

Use a medium or large cookie scoop to portion dough into balls. Optionally roll each ball in granulated sugar before placing them about 2 inches apart on the prepared baking sheet.

Bake at 350 °F for 10–12 minutes—just until edges are set and centers are slightly underbaked. Let cookies cool a few minutes on the sheet before transferring to a wire rack.

Store baked cookies in an airtight container at room temperature for up to one week—or freeze for up to two months.