Preheat oven at 225 F. Line large cookie sheet with parchment paper and insert large piping bag with tip of your choice I use 1 D tip.
Place mixing bowl in the electric stand mixer and attach whisk attachment.
Place egg whites in the mixing bowl and mix on low until the egg white turns foamy. Add in the salt and cream of Tartar. Increase speed to high.
With the mixer of high, gradually add granulated sugar, one fourth cup at a time and mix for one minute in each addition.
Continue to mix on high until the sugar is completely dissolved. The mixture should be double in size. Sugar is completely dissolved when the mixture is not smooth. To test, get s small amount of the mixture and rub it in between your fingers. Mixture is dissolve when you can't feel sugar particles in between your fingers.
Mix on high until the stiff peaks. At his stage, add in vanilla and Ube extract.
Transfer meringue mixture in a large piping bag fitted with 1 D tip. Pipe meringue mixture in the prepared cookie sheet. You can pipe the meringue cookies close to each other since the mixture don't spread.
Bake meringue cookies at 225 F (105 C) for one hour. Don't open the oven while baking. Turn of the oven and leave the meringue cookies in the oven for two more hours. Don't open the oven during this time.