Add plums, jalapeno peppers, sugar, water, 3 tablespoons vinegar and salt to a sauce pan.

Heat to a boil, stirring continuously.

Boil for 6 minutes.

Remove from heat and stir in the remaining 1 tablespoon vinegar.

To make the jam smooth, blend with an immersion blender or when cool, blend in a blender. The fruit will thicken slightly when it cools but will be between a glaze and jam consistency.

Let jam cool then store in refrigerator, bottle or freeze. This will last 2 weeks+ in the refrigerator.