Core, peel and slice the apples and put in a bowl.
Toss the apples with the lemon juice, then add the brown sugar, flour, salt, cinnamon and nutmeg and mix well.
Spray a deep square 8" baking dish with cooking spray and add the apples.
Bake the apples for 15-20 minutes, and then add the topping.
For the topping combine the flour, sugar, baking powder and salt mix well.
Cut the butter into small pieces and cut into the flour, either with a pastry cutter, food processor or two forks. Mix until the mixture is in small crumbs.
Add the buttermilk and stir to just combine.
Drop the topping by spoonfuls on top of the baked apples, in 8 or 9 round blobs.
Sprinkle the topping evenly with the sparkling sugar.
Bake for 25 more minutes, until the topping is golden brown.