Ingredients
4 c. blackberries
2 c. sugar
2 tbsp. lemon juice
2 tsp. lemon zest
Instructions
Start by combining blackberries, sugar, and lemon juice in a large bowl. Use a large spoon or potato masher to crush the berries, then transfer mixture to a medium sauce pan.
Heat sauce pan over medium heat and bring to a boil. Cook, stirring occasionally, until jam is thick, 15 to 20 minutes. Skim any foam that has risen to the surface and stir in lemon zest if using. Transfer to a clean glass jar and let cool completely. Tightly secure lid and refrigerate.