Prepare the berries. Cut the berries into large chunks, discarding any heavily bruised sections. Place a few clean metal spoons in the freezer.

Combine the fruit and sugar in a saucepan. Place the fruit, sugar, lemon, and salt in a heavy-bottomed saucepan over medium heat and mash the fruit a little with a potato masher or large fork into a chunky texture.

Cook the fruit and sugar. Bring the mixture up to a boil, stirring frequently. Continue to boil while keeping an eye on it, still stirring frequently, until the fruit is jammy and thick, about 20 minutes.

Begin checking the fruit for doneness. Start checking to see if the jam is set. Remove a spoon from the freezer and dribble several drops of the jam onto the spoon. Wait a few seconds, and then run a finger through the jam. If it leaves a distinct track in the jam, it is done. If it runs back in on itself, keep cooking the jam and test again a few minutes later.

Cool the jam and move it to two jars. Turn off the heat and carefully transfer the jam into 2 clean glass jars. Seal, label with the fruit and the date. Cool to room temperature and store it in the refrigerator for up to 3 weeks.