• Preheat oven to 350ºF, and spray an 8-inch square baking dish with nonstick cooking spray.
• Prepare the Spiced Apples: In a medium saucepan over medium heat, cook the apples, water, brown sugar, butter and spices together until apples have softened, about 5-10 minutes. Remove from stove and set aside to cool slightly.

Make the Cinnamon-Brown Sugar Filling:

• In a medium bowl combine the butter, brown sugar and cinnamon until smooth; set aside.

Make the Cake:

• In a large bowl, whisk the flour, baking powder, salt, and sugar together until combined. Add the sour cream, milk, eggs, and vanilla, mixing until batter is almost combined. Pour in the melted butter and continue mixing until smooth.
• Spread half of the batter into the prepared pan. Drop spoonfuls of half of the cinnamon-brown sugar filling over the batter. Drop spoonfuls of half of the spiced apples over the batter. Pour the remaining batter on top, followed by spoonfuls of the remaining cinnamon-brown sugar filling and spiced apples. Using a skewer or knife, swirl the mixture into the batter.
• Bake in the oven for 35-40 minutes, or until a toothpick inserted into the center comes out with few crumbs attached. Allow to cool slightly while you make the icing.

Make the Maple Icing:

• In medium bowl, whisk the butter and about half of the powdered sugar together until combined. Whisk in milk/heavy cream, followed by the rest of the powdered sugar. Stir in the maple syrup.
• Spread icing on top of cake. Cut into squares and serve!