Instructions:

• Preheat your oven to 350°F (175°C).
• In a medium mixing bowl, whisk together the all-purpose flour, cornstarch, baking powder, baking soda, and salt. Set aside.
• In a large mixing bowl, beat the softened unsalted butter and granulated sugar together until light and fluffy, about 2-3 minutes.
• Add the room temperature egg and vanilla extract to the butter-sugar mixture and beat until well combined.
• Gradually add the dry ingredient mixture to the wet ingredients, mixing until just combined.
• Gently fold in the rainbow sprinkles until evenly distributed.
• Scoop rounded portions of cookie dough onto a parchment-lined baking sheet, leaving space between each cookie.
• Bake for 10-12 minutes, or until the edges are lightly golden.
• Allow cookies to cool on the baking sheet for about 5 minutes, then transfer to a cooling rack.
• In a mixing bowl, beat the room temperature unsalted butter until creamy. Gradually add the vanilla cake mix, powdered sugar, and vanilla extract, mixing until smooth.
• Add food coloring until desired color is achieved.
• Once the cookies are cooled, spread a generous layer of frosting on each cookie.
• For an extra touch, sprinkle additional rainbow sprinkles on top of the frosted cookies.