How to Make It
Combine baking powder, cinnamon, 1 cup flour, and ¼ cup sugar in a medium bowl. Whisk together milk, melted butter, and egg in a small bowl. Add milk mixture to dry ingredients; stir just until moistened. Set aside.
Toss together berries, lemon juice, salt, and remaining ½ cup sugar and ¼ cup flour in a medium bowl. Transfer berry mixture to a lightly greased (with cooking spray) 5-quart slow cooker. Dollop batter evenly on top; cover and cook on LOW until batter is cooked through, 2 to 2 ½ hours.