Preheat your oven to 100°C (210°F) / 80°C Fan / Gas Mark ¼ and line a large baking tray with parchment paper.
In a spotlessly clean glass or metal bowl, whisk the egg whites, cream of tartar, and salt with an electric mixer on medium speed until soft peaks form.
Begin adding the caster sugar one tablespoon at a time, whisking continuously.
Once all the sugar is incorporated, increase the speed to high and beat until the meringue is thick, stiff, and glossy. You'll know it's ready when you can rub a little between your fingers and not feel any sugar granules.
Spoon the meringue into a piping bag fitted with a large star or fluted nozzle. Pipe six 9cm / 3. 5-inch nests onto your prepared baking tray, creating a small indent in the centre of each.
Bake for 2 hours, or until the meringues are crisp to the touch and lift easily off the parchment.
Turn off the oven and leave the meringues inside with the door ajar to cool completely. This prevents cracking.
Let the meringues cool completely in the turned-off oven. This gradual cooling process helps prevent cracking and ensures a perfectly crisp exterior.
