In a saucepan, combine brown sugar, 1/4 cup flour and 1/4 teaspoon salt. Add water and lemon juice; cook and stir over medium heat until thick. Cover and set aside. , In a bowl, combine baking powder and remaining flour and salt. Cut in 3 tablespoons butter. Add the milk and mix just until moistened (a few lumps will remain); set aside. , Arrange apples in a 1-1/2-quart baking dish; sprinkle with 1/2 teaspoon cinnamon. Add nutmeg, vanilla and remaining butter to sauce; pour over apples. Drop dough by spoonfuls over sauce. Combine remaining cinnamon and coarse sugar; sprinkle over dough. Bake at 350° until top is brown and apples are tender, about 55 minutes. Serve warm, with whipped cream if desired.