Cream together butter and cream cheese. Add sugar and eggs, beat well. Add vanilla. Sift flour, salt, baking powder, and baking soda together in a separate bowl. Add to the cream cheese batter alternately with milk. Stir in diced apples. Batter will be very thick. Spoon into greased and floured 9x13-inch pan. Prepare the topping by combining the flour, sugar, and cinnamon, and mixing well. Cut in butter in small pieces until it is the size of small peas and is evenly distributed. Sprinkle the topping mixture evenly over batter. Bake at 350 degrees For 50 to 60 minutes. Let cool at least 20 minutes before slicing.