This homemade blackberry jam recipe only needs 4 ingredients and will help you preserve the flavors of summer to enjoy all year! 2 cups fresh blackberries 6 tablespoons granulated sugar 1 teaspoon grated lemon zest 2 tablespoons lemon juice Combine blackberries, granulated sugar and lemon juice in a medium saucepan. Bring to a simmer over medium-low heat. Cook until the berries start to soften, about 1 minute, stir frequently. Simmer until the mixture has a jamlike consistency, about 8-10 minute