In a medium saucepan, combine apples, 2 tablespoons (30 grams) cider, brown sugar, vanilla, lemon juice, and salt. Cook over medium-high heat, stirring frequently, until apples begin to soften and break down, 8 to 10 minutes.

Stir remaining 3 cups (720 grams) cider into apple mixture. Bring to a boil over medium-high heat; cook, stirring frequently and mashing apples with a spoon, until mixture is thickened and liquid is almost completely evaporated, 20 to25 minutes.

Remove from heat, and let cool completely. Refrigerate until cold before using, at least 1 hour or up to 1 week.