Directions

1. Preheat oven to 350 degrees.
2. Melt butter in a large cast-iron skillet or ovenproof baking dish, in the oven, 5 to 7 minutes.
3. Meanwhile, place blackberries in a large bowl. Using a potato masher, mash blackberries to release their juices. If blackberries are tart, sprinkle with sugar.
4. In another large bowl, whisk together flour, baking powder, and salt. Add 1 cup sugar, milk, and vanilla extract; mix until well combined. Remove skillet from oven and add melted butter to flour mixture; stir to combine. Pour mixture into skillet and pour blackberries and their juices into the center.
5. Transfer skillet to oven and bake until top is golden brown and a cake tester inserted into the batter comes out clean, about 1 hour. Serve hot, warm, or at room temperature with whipped cream, creme fraiche, or ice cream.