Bring the water with the brown sugar to the boil. Add the zest of an organic lemon. Make sure to only use the yellow part of the bowl, as the white skin underneath can make the lemonade bitter. The pinch of salt rounds off the taste.
After the sugar has dissolved, add the juice of five lemons (one lemon makes about 70 ml of juice). Let the mixture simmer for about 10 minutes and then immediately pour into a clean glass bottle, close tightly and refrigerate.
The syrup becomes thicker as it cools. The syrup is mixed with mineral water in a ratio of 1:10.