Rhubarb Jam

Bring rhubarb, sugar, and 1/4 teaspoon salt to a boil in a large pot, stirring often. Cook, stirring often, until bubbles slow, foam subsides, fruit rises to the top, and jam sticks to a wooden or metal spoon when lifted from mixture, about 10 minutes. Stir in lemon juice to taste. Let cool for 1 hour. Refrigerate overnight.