In a large bowl, combine the blueberries, 1/2 cup sugar, cornstarch, lemon juice, cinnamon and nutmeg. Transfer to a 2-qt. baking dish coated with cooking spray. , In a small bowl, combine the flour, lemon zest, baking powder, salt, baking soda and remaining sugar; cut in butter until mixture resembles coarse crumbs. Stir in buttermilk just until moistened. Drop by tablespoonfuls onto blueberry mixture. , Bake, uncovered, at 375° for 30-35 minutes or until golden brown. Serve warm.