• Place a large pot with water over medium-high heat, once it is boiling, blanch the peaches for 1 minute.
• After 1 minute, put them immediately into a cold water bath, for another minute only. No longer.
• Peel off the skins set the peaches aside.
• Slice the peaches in half, remove the pit, and after that slice the peaches.

Make the Jam:

• Add the peach slices, lemon zest, lemon juice, and vanilla, into a heavy-bottomed large pot, over medium-low heat.
• Cook for about 15 minutes, until the peaches are soft, and the juices are released.
• Add the sugar, and stir into the mixture until dissolved.
• Increase heat to medium-high and bring the mixture to a boil, cook for 5 minutes, stirring continuously.
• After the 5 minutes, reduce the heat to low-medium, and slowly cook for another 40-60 minutes, not boiling. The jam is ready when the mixture is thick enough to leave a trail behind the spoon.
• Remove from heat, and let the jam cool completely before serving.
• Add them to mason jars and refrigerate.