Preheat the oven to 375 degrees F.
For the filling:
In a large mixing bowl, combine the sugar, spices, salt, and cornstarch. Add the fruit and mix the coating evenly with the sugar mixture. Toss with the lemon juice. Place the fruit filling in a 10 or 12-inch cast iron skillet or a 2-quart baking dish and place in the oven for 20 minutes. In the meantime, make the biscuit dough.
For the topping:
Whisk the flour, sugar, baking powder, salt, and baking soda in a large mixing bowl. Using a food processor, pastry cutter, or your fingertips incorporate 3/4 cup chilled butter into the dry ingredients until the mixture resembles coarse meal. Add the buttermilk and stir just until moistened.
Remove the fruit from the oven and drop 6 to 8 (1/2-cup) portions of the biscuit dough on top of the cooked fruit, spacing the mounds about a 1/2-inch apart.
Increase the oven temperature to 425 degrees F and bake until the biscuits are golden brown on top and the fruit is bubbling, about 15 to 20 minutes. Remove the cobbler from the oven and cool for 15 minutes before serving.
To make biscuit:
Preheat the oven to 425 degrees F. Line a baking sheet with parchment paper.
Whisk the flour, sugar, baking powder, salt, and baking soda in a large mixing bowl.
Using a food processor, pastry cutter, or your fingertips incorporate 3/4 cup chilled butter into the dry ingredients until the mixture resembles coarse meal.
Add the buttermilk and stir just until moistened. Using 1/2 cup dough for each biscuit, drop the biscuits onto the prepared baking sheet, spacing mounds about 2-inches apart.
Bake the biscuits until they are golden brown on top, about 15 to 20 minutes or until a tester comes out clean. Serve the biscuits warm.
Seasoning Your Cast Iron Skillet
Position a rack in the center of the oven, and preheat the oven to 325 degrees F.
Wash the skillet with warm, soapy water and dry thoroughly.
Apply a thin coating of vegetable oil or vegetable shortening with a paper towel on all surfaces, inside and out.
Place the skillet on the oven rack, upside down. Place a baking sheet or a sheet of foil on the rack beneath to catch any dripping.
Bake for 1 hour, then turn off the heat, open the door, and allow the skillet to cool inside the oven before removing. The skillet is now ready to use.
To wash: Scrub the skillet with hot water and a brush without detergent. Never use sharp or metal utensils on it while cooking and never place in the dishwasher.