01 -
Preheat oven to 350°F (175°C). Grease a 9x13-inch baking dish.
02 -
Mix cake mix, melted butter, water, and eggs until smooth.
03 -
Pour half the batter into the baking dish.
04 -
Spoon apple pie filling over batter, spread. Sprinkle cinnamon.
05 -
Combine brown sugar, oats, flour, and nuts (if using) in a bowl.
06 -
Sprinkle oat mixture over apple layer.
07 -
Pour remaining batter over the top, spread gently.
08 -
Bake 30-35 minutes until toothpick comes out clean.
09 -
Mix powdered sugar with milk until smooth.
10 -
Cool slightly, drizzle glaze. Let set before serving.
11 -
Slice and serve warm with coffee or tea.