Prepare the peaches by peeling and slicing/chopping. Whatever your preference is! Place in a bowl and cover with 1/3 cup sugar. Allow to sit for 30 minutes. Strain off the peach juices that formed and set aside prepared peaches.
Add peach juice with lemon juice, and enough water to create 1/2 cup liquid total.
In a small sauce pan, combine cornstarch, salt, and peach juice. Bring to a simmer and allow to thicken, stirring continually! Do not leave unattended.
Stir in butter and allow to chill slightly before combining with the peaches.