Preheat the oven to 200°F and line two flat, untextured baking sheets with parchment paper, and set aside.
Squeeze lemon juice onto a paper towel and rub the inside of a stand mixer bowl to make sure it is completely free of grease before starting.
Add the egg whites and cream of tartar to the bowl and beat with a whisk attachment on low speed until it becomes foamy then increase speed to high.
Add the sugar 1 tablespoon at a time, mixing for about 15 seconds between each addition to let it dissolve. Once all of the sugar is added, continue beating at high speed until the mixture is thick and shiny.
When ready, the meringue should form stiff peaks and the sugar should be completely dissolved. To taste for readiness, rub a small amount of meringue between your fingers to make sure it's not gritty. If it is, continue mixing until it feels smooth, this can take up to 10 minutes more.
Stir in the vanilla extract and food coloring at low speed until evenly blended.
Dip each lollipop stick about ⅓ to ½ into the meringue mixture and place on the prepared baking sheets, leaving ample room between each to pipe on the cookies. If making cookies you can omit this step.
Transfer the meringue to a large piping bag fitted with a large tip of your choice (I recommend round, star, or flat tip. You can also use a small tip to make cookies instead of pops.
Making Pops: Pipe the meringue onto the dip end of the stick, starting at the midpoint of the stick with long lines and shorting them as you work your way to the tip of the stick to create a triangular tree shape.
Making Cookies: Omit the sticks and pipe the meringue into a triangle starting with larger lines and shortening your strokes as you pipe.
Add sprinkles before baking if desired.
Bake for 1 hour, then turn off the oven (do not open the door) and allow the cooking to cool completely in the oven, about 1 to 2 hours more.
The cookies should be crisp and dry when done (not tacky) and very airy.