• 1 10-ounce bag frozen blackberries, thawed
• 3 tablespoons fresh lemon juice
• 2 tablespoons sugar
• 1 cup pure maple syrup

Bring blackberries, lemon juice, and sugar to a boil in a medium saucepan. Reduce heat and simmer, stirring occasionally, until berries soften and juices thicken slightly, 10–15 minutes. Remove from heat; stir in maple syrup. Let cool slightly before serving.

DO AHEAD: Syrup can be made 1 day ahead. Let cool; cover and chill.