1. Whip the egg whites with a pinch of salt to foam.
2. Slowly incorporate the sugar. When the sugar has fully dissolved, increase the mixing speed.
3. By using a spoon, add powdered sugar and cornstarch (mixed together) and whip until the mass becomes thick and shiny. At the very end, pour some lemon juice and whip for 30 more seconds.
4. Put the mixture into the pastry bag with the pastry nozzle and make the meringue by creating round shapes, like nests.
5. Put them directly in the oven at 90-100°C. Bake them for an hour, an hour and a half.
*If you have a gas oven which you can't control the temperature of, bake the meringue at the lowest temperature. Keep the door cracked open, so they won't burn, and make sure to check on them in the process