Toss berries with sugar and salt in a medium bowl. Let them stand for about 30 minutes to dissolve sugar, tossing occasionally.
Meanwhile, process jam in food processor until smooth; transfer to small saucepan. Bring jam to simmer over medium-high heat. Cook, stirring frequently until dark and no longer frothy, about 3 minutes. Stir in lemon juice; pour over strawberries and stir to combine. Let cool, then cover with plastic wrap and refrigerate until cold, at least 2 hours or up to 12 hours.
To serve, spoon a portion of topping over each slice of cheesecake, poundcake or scoop of vanilla ice cream!