Preheat the oven to 100 degrees Celsius (212 degrees Fahrenheit), fan.
Put the egg whites in a bowl and preferably use a stand mixer to whisk them stiff.
Add the sugar bit by bit and keep whisking until the mixture is firm/smooth/stiff. You should be able to turn the bowl upside down without it falling out. This can easily take up to 10 minutes.
When you have added half of the sugar, add the vinegar.
When it is stiff, add the salt and whisk for another minute.
Put baking paper on a baking tray and draw a circle with a radius of approximately 20-22 cm on it.
Pour the meringue onto the baking tray and use a spatula to spread it out, keeping it within the circle.Bake it for 2 hours and then turn off the oven.
Let it sit and dry while the oven cools down. This can be overnight.