1. Preheat oven to 450°. Stir together cornmeal and sugar in a large bowl; make a well in center of mixture. Whisk together eggs, sour cream, and oil; add to cornmeal mixture, stirring just until dry ingredients are moistened. Fold in blackberries. Spoon batter into a lightly greased 12-inch cast-iron skillet.
2. Bake at 450° for 30 minutes or until a wooden pick inserted in center comes out clean, shielding with aluminum foil after 25 minutes to prevent excessive browning, if necessary.
Blackberry Cornbread Muffins: Prepare batter as directed. Coat 2 muffin pans with vegetable cooking spray; spoon batter into muffin pans, filling three-fourths full. Bake at 450° for 15 to 17 minutes or until tops are golden brown. Cool in pan on a wire rack 5 minutes. Remove from pan to wire rack. Makes 2 dozen muffins. Bake: 15 min. Cool: 5 min.