Add the strawberries, sugar, lemon juice, and salt to a saucepan. Cook over medium-low heat for 12–18 minutes, stirring often and mashing the berries until thick and jammy. Cool completely.
Reserve ½ cup jam for the base and ½ cup for swirling.
Line a loaf pan with parchment paper and chill.
Whisk together the sweetened condensed milk, vanilla, salt, and ½ cup cooled strawberry jam.
Whip the cold heavy cream to stiff peaks.
Fold one-third of the whipped cream into the strawberry mixture, then gently fold in the remaining whipped cream.
Layer the ice cream mixture into the loaf pan, adding spoonfuls of the reserved strawberry jam between layers. Finish with more jam and gently swirl with a butter knife.
Cover and freeze for 6–8 hours or overnight.
Let sit at room temperature for 5–10 minutes before scooping.