Trace five 4 inch circles on parchment paper and preheat oven to 300F.
Whip the egg whites, salt, and cream of tartar to medium-stiff peaks. Be careful not to over whip! (zoë has an instagram highlight with descriptions on the peaks or you can use the kitchn's guide to egg white peaks)
Add in the water and drizzle in sugar while whipping on a low speed. Then, turn up the speed and whip until stiff peaks.
Fold in the vinegar, corn starch, and vanilla extract with a spatula making sure not to knock out any air.
Scoop the meringue out onto the parchment circles. Shape the meringue into circles using the spatula. Clean the edges of the circle with your finger or a paper towel. (you can also shape them further by taking a knife or offset spatula, holding it parallel to the meringue and lifting upwards. go around the circle while overlapping the vertical strokes.) Indent the pavlova at the top.
Bake for 30 minutes at 300F and then decrease the oven to 275F and bake for 45 minutes. Do not open the oven or the pavlova will crack. Leave pavlova to cool in the oven for 1 hour or overnight with the oven light on. (I prefer to cool overnight). The pavlova will collapse in the center and give you a place for delicious fillings.