Preheat oven to 350. Prepare cake mix as package directs, stir in apples.
Pour into well-greased and floured 13x9 inch baking pan. Bake for 30 minutes or until wooden pick inserted near center comes out clean.
Meanwhile, in medium bowl, combine sweetened condensed milk, sour cream and Realemon juice. Remove cake from oven; spread cream mixture over top.
Return to oven; bake 10 minutes longer or until set. Sprinkle with cinnamon. Cool. Garnish as desired. Refrigerate leftovers.