Preheat oven to 150°C. Draw a 22cm circle on a sheet of non-stick baking paper and place, marked side down on a large greased baking tray.
Drain chickpea water through a fine sieve into a large mixing bowl. Using electric beaters on a low setting, whisk until foamy. Add apple cider vinegar and whisk on medium until soft peaks form.
Add 1/3 a cup of caster sugar and continue to whisk until mixture becomes glossy. Gradually add the remainder of the sugar, tbsp at a time, whisking until meringue is thick and glossy.
Gently fold in vanilla extract and sift cornflour.
Drop large spoonfuls of meringue on the tray using the circle as a guide. Reduce the oven to 110°C. Bake for 1.5 - 2 hours. Turn the oven off, leave the pavlova to cool completely in the oven with the door closed.