Preheat oven to 375° F. Prepare a muffin tin with vegetable oil (you can use paper liners with a light coating of nonstick spray, but be aware that these muffins may stick to paper.) In a large bowl, beat together the milk, lime juice, vegetable oil and eggs until completely combined. The lime juice may cause the milk to separate, but it is fine. Slowly stir in cornbread mix, stirring well until completely combined. Set batter aside. Coat blackberries completely in powdered sugar – shaking them together in a plastic bag works well. Add coated blackberries, the rest of the powdered sugar, and the lime zest to the batter, and stir gently just until evenly combined – stop as soon as you see purple color bleeding from the blackberries. Spoon the batter into the muffin cups until about ¾ to almost completely full, distributing blackberries as evenly as possible. Bake 18-22 minutes or until tops are lightly browned. Let cool on a wire rack. Serve warm (preferably with butter and honey).
Notes: If you’d like to make these sweeter, you can sprinkle the tops with crystal sprinkling sugar before baking. These are best enjoyed the day they are made, but will keep 1 day in a tightly sealed container.