Preheat your oven to 225°F (110°C) and line two baking sheets with parchment paper or silicone mats.

In a clean mixing bowl, add the egg whites and cream of tartar, then beat at medium speed until soft peaks form, about 2-3 minutes.

Increase the mixer speed to high and gradually add the granulated sugar until you achieve stiff peaks, about 5-7 minutes.

Gently fold in your chosen Jello powder until evenly combined, preserving the airy texture.

Transfer the meringue mixture into a piping bag or spoon mounds onto the prepared baking sheets, about 1 inch apart.

Bake for 1.5 to 2 hours until dry to the touch, avoiding opening the oven door during baking.

Turn off the oven and leave the cookies inside for an additional hour to cool.

Transfer cooled cookies to an airtight container to store at room temperature.