Preheat oven to 375°F. Lightly spray an 8 or 9-inch baking dish with nonstick cooking spray and set aside.
In a medium bowl combine all purpose flour, brown sugar, salt, baking powder and cinnamon. Whisk to combine.
Add the melted butter and stir with a fork until crumbly.
In a large bowl, combine apples, granulated sugar, lemon juice, cornstarch (or flour if using) and ground cinnamon.
Transfer apple mixture to the prepared baking dish and spread into an even layer.
Sprinkle crumble mixture evenly over the top of the filling.
Bake for 35 to 45 minutes or until bubbling and golden brown on top.
Let cool for 15 minutes before serving with ice cream if desired.