Combine 1 cup blueberries, maple syrup, cinnamon, and salt in small saucepan. Bring to boil over medium-high heat. Mash blueberries with potato masher and cook, stirring frequently, until blueberries have broken down and mixture is reduced and slightly thickened, about 5 minutes.
Off heat, stir in butter, lemon zest and juice, and remaining ½ cup blueberries until butter is melted and blueberries are softened, about 1 minute. Serve.