12 ounces mixed strawberries and raspberries, hulled and chopped
1/4 cup water
6 tablespoons granulated sugar
Pinch of sea salt
2 teaspoons lemon juice
Combine berries, water, sugar and salt in a medium saucepan over medium-high heat. Cook, while stirring, until berries break down, about 5 minutes.
Transfer to a food processor and process until smooth. Strain through a fine mesh sieve into a bowl, pressing down with a rubber spatula to extract as much berry puree as possible. Discard seeds from the sieve.
Stir in lemon juice. Cover and refrigerate until chilled, about 1 hour.