Preheat your oven to 275°F (135°C) to ensure a crispy meringue.
Line a baking sheet with parchment paper, drawing a circle as a guide for the pavlova.
In a clean mixing bowl, whip the egg whites until frothy, then increase speed to high until stiff peaks form (about 5-7 minutes).
Gradually add the superfine sweetener, followed by cornstarch, vinegar, and vanilla. Beat until shiny and well combined.
Spoon the meringue onto the prepared parchment, shaping it into a round disc with a slight indentation in the center.
Bake for about 1 hour and 15 minutes until dry to the touch. Leave in the oven to cool completely.
Whip the cream with sugar-free powdered sugar until soft peaks form, being careful not to over-whip.
Once the pavlova is cool, remove it from parchment, fill with whipped cream, and top with berries.
