Set oven to 350º and grease and flour 2 8 or 9-inch round cake pans. If you have parchment paper, line the bottoms with parchment rounds to make it even easier to get them out.
Combine the filling ingredients in a small bowl and set aside.
In a large mixing bowl, combine all dry ingredients with a whisk.
Add eggs, milk and vanilla and mix on medium speed for about 2 minutes, until smooth and creamy looking.
Cut the butter into tablespoons and add it to the batter. Beat together on low speed for one minute, scrape the sides, then beat on medium high for 1 1/2 minutes. Scrape the bowl and finish mixing for 30 seconds on low speed.
Divide dough evenly between the two pans. Spread apple mixture evenly over ONE of the cakes.
Bake cakes for 15-20 minutes or until a toothpick inserted in the center comes out clean.
Allow to cook in pans 10 minutes, then turn onto racks (right sides up) to finish cooling.
Make cinnamon cream cheese frosting: Beat cheese, butter, cinnamon and vanilla together on medium speed until well blended. Sift in powdered sugar by the half-cup until the texture is as you like it.
Stack the plain cake on top of the apple cake so that the apple filling is in the center. Frost with cinnamon cream cheese frosting.