In a small saucepan, add the butter, brown sugar, cinnamon and melt them, stirring constantly until smooth. Pour the caramel into a greased 9-inch baking dish.
Peel the apples, cut into thin slices and lay on top of the caramel.
In a large bowl, whisk softened butter and sugar, then add eggs and vanilla, one at a time.
In a separate bowl, combine flour, salt, baking powder, and cinnamon.
Add flour and milk to the butter mixture, alternating, in small portions, whisk after each addition, starting and ending with flour. Pour the dough over the apples, spread with a spatula. Bake 35-40 minutes, or until a toothpick comes out clean.
Remove the pie from the oven, let cool for 10-15 minutes, cover with a large flat dish, and turn upside down.