Wash and cut off the tips of the Lemon (12), then cut them in half and in thin slices
Remove pits and any black-ish parts of the skin
Place the sliced lemons into a large bowl, cover with water and let it marinate for 24 hours.
After this time has passed, take the lemons off the water and place them in a large pot. Add the Granulated Sugar (800 gram) and Water (600 milliliter).
Bring to a simmer and cook on very low heat, stirring frequently for a couple of hours. As lemons are very high in natural pectine, the jam will thicken very fast, so keep an eye on it and stir as much as you can to avoid the jam to stick to the pot.
When ready, immediately divide the jam into sterilized jars, close them tight with a lid and place the jars upside down covered with a towel until completely cooled. Store the jars in a dry and cool place, which would allow them to last for months.