Cast-Iron Apple Cobbler

1 1/2 cupsflour, divided
4 pounds Fuji apples, thinly sliced peeled
2/3 cup sugar, divided
2 tablespoons butter, melted
2 teaspoons vanilla extract
3/4 teaspoon salt, divided
1/2 teaspoon ground cinnamon
1/4 teaspoon ground nutmeg
1/2 cup water
2 teaspoons baking powder
1/4 cup chilled butter, cut into small pieces
1 cup low-fat buttermilk

Combine 1/2 cup flour, apple, 1/3 cup sugar, 2 tablespoons butter, vanilla, 1/2 teaspoon salt, cinnamon, and nutmeg in a large bowl, tossing well. Spoon into a large cast-iron Dutch oven. Add 1/2 cup water.

Combine remaining flour, remaining 1/3 cup sugar, remaining 1/4 teaspoon salt, and baking powder in a medium bowl; cut in 1/4 cup butter with a pastry blender or 2 knives until mixture resembles coarse meal. Add buttermilk; stir until just moist. Drop batter by tablespoonfuls over apple mixture. Bake at 375° for 1 hour or until bubbly and browned. Serve warm.