1. Preheat oven to 350°F.
2. Unroll one pie crust and place it in the bottom and up the sides of a 12-inch cast iron skillet. Pierce the bottom and sides of the crust with a fork.
3. Bake for 7 minutes, then remove from the oven and increase the oven temperature to 400°F.
4. In a large bowl, mix melted butter, 1⅓ cups sugar, and flour.
5. Add the blackberries to the bowl with the butter/sugar/flour mixture and toss until the berries are covered and the mixture is crumbly.
6. Gently pour the berry mixture into the skillet and sprinkle water over the berries.