Cut the lemons into slices and put them in the pan, pour in the water and bring to a boil. Also sterilize the jars by soaking them in water (over the heat) for 30 minutes.

Place the lemons in a bowl and blend them in a blender or food processor, then pour them into a saucepan and place the first half of the sugar, then place the rest. Also add the vanilla extract and bring to a very low heat for 30 minutes. Then pour into the jars, close them and turn them upside down. Let them cool completely.