This is delicious spooned over ice cream and fresh fruit, or as an accompaniment to our Berry Vacherin.
Combine raspberries, sugar, lemon juice, and salt in a small, nonreactive saucepan over low heat. Cook until berries release their juice and just start to break down, about 5 minutes. Use a rubber spatula to press berries through a fine sieve; discard solids. Let cool, and refrigerate until ready to use.