Preheat oven to 275 °F.
Line two baking sheets with parchment paper.
Place egg whites in a bowl and whisk with an electric mixer on medium for 5 minutes. Then increase to high and mix until stiff peaks form.
Add sugar slowly, one tablespoon at a time mixing well between each addition.
Once all sugar has been added whisk for 5 minutes until the meringue is glossy and stiff.
Scrape down the sides of the bowl and add the salt and vinegar. Mix for another 2 minutes.
Fill a piping bag with a tip, with half of the mixture and pipe into swirls.
Repeat with the rest of the meringue mixture.
Turn oven down to 250 °F and place the baking sheets in the oven.
Bake for 1½ hours. Turn the oven off and and leave the meringues in the oven as it cools down.
When the oven is cool, remove the meringues and gently remove them from parchment paper.
