Preheat oven to 135C/275F/Gas 1.
In a clean bowl, mix the egg whites and salt until stiff. Add the sugar one tablespoon at a time, whisking until very stiff and glossy, then beat in the cornflour, vinegar and vanilla.
Butter a shallow ovenproof dish and fill with the meringue, hollowing out the centre to form a nest shape.
Bake for one and a quarter hours, remove and cool.
When cool, fill the hollow meringue with the whipped cream and top with the prepared fruit. Serve.
