Set the oven to 225°F. Line a baking sheet with parchment paper.

Beat egg whites, salt, and cream of tartar on medium speed until soft peaks form. The mixture should be foamy but still droop at the tip.

Gradually add sugar and Jello powder, one tablespoon at a time. Increase the speed to high and whip until stiff, glossy peaks form (5-7 minutes).

Transfer the meringue to a piping bag with a 1M star tip. Pipe rosettes or small swirls onto the baking sheet, spacing them apart.

Bake for 1 hour at 225°F. Do not open the oven door. After 1 hour, turn off the oven and let the cookies dry inside for another hour.

Once cooled, gently peel the meringues off the parchment. Store in an airtight container or serve immediately.