Combine the berries, sugar, and lemon zest in a medium-sized saucepan and set over medium heat. When mixture starts to bubble, turn heat to medium-low and cook 5 minutes more, stirring and smashing berries as they cook. Push hot berry mixture through a fine mesh sieve to remove seeds. This is slow work and berries are very seedy. Use a large wooden spoon and keep pushing until all you’re left with is a sticky mix of seeds and pulp. Discard seed mixture. Allow the juice to cool to room temp or set in the fridge for 20 minutes.

In a medium-sized bowl, stir the condensed milk into the berry juice. Add vanilla, lemon juice, and sea salt.

In a large bowl, whip the heavy cream to soft peaks. Fold the berry mixture in with the cream.

Spoon into a metal loaf pan, cover with a lid or plastic wrap, and freeze for at least 4 hours.