Start by beating together your egg whites until stiff peaks form. Slowly, add the superfine sweetener, one tablespoon at a time, until the meringue is glossy and thick. Finally, add the vinegar, cornstarch, and vanilla extract, and beat until just combined. Gently transfer the mixture onto a baking sheet lined with foil. Form a circular shape, keeping the sides thicker. Bake in a preheated oven for around 90 minutes, or until dry and tender. Turn off the oven but keep the pavlova in there to cool completely.
Once the pavlova has cooled, beat together the heavy cream and powdered sugar until combined and smooth. Spread over the top of the pavlova and decorate with berries or other low carb fruit. Refrigerate for 30 minutes, for the cream to chill.