1. Preheat your oven to 200°F (95°C) and line a baking sheet with parchment paper. Prepare a piping bag fitted with a large star tip (like Wilton 1M).

2. In a clean, dry bowl, beat egg whites on medium speed until foamy. Add cream of tartar and continue beating until soft peaks form.

3. Slowly add sugar, one tablespoon at a time, while beating on medium-high until stiff, glossy peaks form.

4. Gently fold in vanilla extract and food coloring (if using), being careful not to deflate the meringue.

5. Place cookie bases on the baking sheet. Fill the piping bag with meringue and pipe spirals to form tree shapes on each cookie base.

6. Bake for 1.5 to 2 hours, or until meringues are dry to the touch. Turn off the oven and let them cool inside for another hour.

7. Once fully cooled, decorate with sprinkles, powdered sugar, or edible glitter if desired. Store in an airtight container away from moisture.