Combine all ingredients, except apples and topping, in large bowl and mix on medium for 5-10 minutes (the longer you mix the "fluffier" your cake will be).
While cake batter is mixing, peel, core & slice apples. In bottom of 15x10 pan, cover bottom with thin layer of brown sugar and cinnamon. Layer apples over top. Pour batter on top of apples, making sure all apples are covered. Bake at 35o for 45 min - 55 min. Use "toothpick test" to confirm cake is done. Cool for 20-30 minutes and then "flip" into a serving dish.