Preheat oven to 350 degrees. Spray 9x13 baking dish with nonstick cooking spray.
Measure out 2 cups of the cake mix. Put aside the leftover cake mix.
In a mixing bowl combine the 2 cups of cake mix, along with the flour and yeast. Stir until combined. Then pour in warm water and stir well. Next add eggs and stir. Batter will be pretty lumpy and thick.
Spread the mixture into the prepared baking dish. The mixture will be kinda stretchy because of the yeast.
Then spread both cans of pie filling on top of cake batter. Try to spread out evenly.
In a bowl combine the rest of the cake mix that was set aside with cubed butter. Use pastry cutter or fork or even your hands. It should be clumpy.
Sprinkle this topping mixture over the pie filling. Then bake for 45 - 55 minutes. Toppjng should be golden brown. Allow cake to cool for 10 to 15 minutes.
In a bowl combine powdered sugar and milk. Start with smaller amount of milk and then add more until the desired consistency. Drizzle icing over the top of cake.