Add strawberries, sugar, lemon juice, and a pinch of salt to a heavy-bottomed pot and cook the mixture over a medium heat. As the fruit begins to soften, mash the fruit with a potato masher. Place 2-3 metal spoons in the freezer.
Bring the mixture to a boil and stir frequently. Cook until the mixture thickens, about 20 minutes.
To check for doneness, dip one of the frozen spoons in the mixture. If you can drag your finger across and the jam holds its form, it is done.
Transfer the mixture to a 2 8-ounce mason jars and let cool. Seal and keep in the fridge for up to 3 weeks.