Preheat your oven to 100°C.
Pour the egg whites and salt into the bowl of your food processor with the whipping attachment.
Start whipping the egg whites at medium speed. When they become frothy, start pouring in the sugar a little at a time. Then add a few drops of lemon juice/white vinegar while continuing to beat. Stop beating when the whites are stiff. When you remove your beaters from the meringue, a peak should form at the end.
Place parchment paper on a baking sheet. Using a pastry bag, pipe small piles in a staggered pattern so they don't touch each other. Bake for 1 hour. Every 20 minutes, ajar the oven door to let the steam escape. Watch regularly. To see if the meringues are done, try peeling one off. At the end of baking, leave the door barely ajar and let the meringues cool in the oven. Then carefully remove the meringues from the paper.