1. Preheat oven to 200°F (95°C) and line two baking sheets with parchment paper.

2. In a large, clean mixing bowl, beat egg whites on medium speed until frothy.

3. Add cream of tartar and continue beating until soft peaks form.

4. Slowly add the sugar, one tablespoon at a time, beating continuously until stiff, glossy peaks form.

5. Add the Jello powder and vanilla extract (if using), and beat just until incorporated.

6. If desired, divide meringue into portions and mix in different flavors/colors.

7. Transfer meringue to a piping bag with a round or star tip. Pipe small swirls onto baking sheets.

8. Bake for 1.5 to 2 hours, until cookies are dry to the touch and lift off parchment easily.

9. Turn off the oven and let cookies cool inside with the door slightly open for 30 minutes.

10. Store in an airtight container at room temperature for up to 1 week.