Preheat oven to 350 degrees and prepare a 9x13 baking dish with non-stick spray. Optional: line the dish with foil and spray the foil with non-stick spray for easy removal.
In a large bowl, cream together the butter, sugar and vanilla. Add in the eggs, one at a time, and mix until well combined.
Over the same bowl, sift the flour and baking powder. Mix the wet and dry together until well combined.
Pour 3/4 of the batter into the baking dish and press it out evenly on the bottom. Spread 1 1/2 cans of the apple pie filling all along the crust, and then sprinkle with all spice and the pecans (optional).
Take the remaining batter and spoon it over the top of the pie filling, spread it out in an uneven way. Bake for 30-40 minutes, until the top is golden brown. Set out to cool while you prepare the glaze.
In a small bowl, mix together the powdered sugar and heavy cream until well incorporated. Add more cream if you want a thinner consistency. Drizzle over the top.
Best-served same day and perfect with a side of ice cream.