In a small bowl combine the brown sugar, cinnamon, and salt.
Stir in the melted butter.
Gently mix in the flour until crumbles start to form. Be careful not the overmix. Set aside
Preheat your oven to 350F. Spray a 9x13 pan with non-stick spray and line with parchment paper.
In a large bowl combine the flour, sugar, baking powder, and salt. Whisk until free of lumps.
In a medium bowl combine the melted butter, eggs, vanilla, and milk.
Mix the wet and dry ingredients until just combined.
Pour the batter into the prepared pan.
In a small bowl combine the diced apples and ground cinnamon.
Spread the apples evenly over the batter.
Spread the crumble topping evenly over the apples.
Place in oven and bake for 30-35 minutes or until a toothpick inserted into the center comes out with only a few moist crumbs
Remove from oven and allow to cool slightly before slicing.