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

In a large mixing bowl, combine egg whites and cream of tartar. Beat on medium speed until soft peaks form, about 2-3 minutes.

Slowly add granulated sugar, one tablespoon at a time, while continuing to beat the egg whites on medium-high speed for 4-5 minutes until stiff, glossy peaks form.

Gently fold the Jello powder into the meringue mixture using a spatula until fully integrated.

Transfer the meringue mixture to a piping bag or use a spoon. Pipe small dollops onto the prepared baking sheets, spaced about one inch apart.

Bake in the preheated oven for 1.5 to 2 hours until dry to the touch, then turn off the oven and let cookies cool inside for an additional hour.

Carefully remove the cookies from the baking sheets and serve fresh or store in an airtight container.