1. Heat oven to 350 degrees F. Grease a 2-1/2-quart baking dish. Set aside.
2. For filling, combine blueberries, 3/4 cup sugar, lemon peel and juice, cinnamon, and tapioca in a large bowl. Let stand 15 minutes.
3. For topping, combine flour, cornmeal, the 1/3 cup sugar, the baking powder, baking soda and salt in another large bowl. With a pastry blender or 2 knives, cut in butter until mixture resembles coarse crumbs. Stir in buttermilk with a rubber spatula just until blended.
4. Transfer filling to prepared baking dish. Drop topping by tablespoonfuls over blueberries. Sprinkle cinnamon-sugar mixture evenly over topping. Bake 55 to 60 minutes or until topping is golden and filling is bubbly. Cool on a wire rack 30 minutes. Serve with ice cream, if desired. Makes 8 servings.