For the pavlova, preheat the oven to 120 °C (250 °F). Cover a baking tray with baking paper and draw 2 Ø 20 cm (8'') circles with a pencil. Turn the baking paper over (so that the pavlova does not come into contact with the pencil).
Put aquafaba and cream of tartar in a large bowl and beat with a hand mixer at medium-high speed until stiff peaks form (about 7-8 minutes).
Then, every 60 seconds, add 1 tablespoon of powdered sugar, and continue beating until dissolved. Be aware, if the sugar is added faster, the pavlova will collapse in the oven.
Once all the powdered sugar has been added, continue beating for 2 minutes.
Add xanthan gum and cornstarch and continue beating for 1 minute until combined.
Spoon the pavlova mixture onto the 2 circles (1 if you are making a pavlova with a single layer of meringue) and shape as desired.
Bake the meringues in the middle of the oven for 45 minutes, then reduce the temperature to 100 °C (200 °F) and bake for another 75 minutes.
Then turn off the oven and let them cool in the oven overnight.