Prep: Preheat your oven to 350° F. Place a piece of parchment paper across the bottom of a 9-inch springform or loose-bottom pan. Spray the inside of the pan with nonstick spray.

Make the Apple Filling:  Add all the apple filling ingredients except the corn starch and water to a large saucepan. Cook over medium-high heat, stirring regularly, for about 8-10 minutes---or until the apples are tender and the mixture has caramelized.

Stir together the cornstarch and water in a small bowl until dissolved, and then stir into the apples over medium-high heat. Cook for 1-2 minutes, until the juices thicken up. Remove from heat and set aside to cool.

Make the Cake Batter:  Melt the butter in a large mixing bowl. Whisk in the oil, then the sugars, and then the eggs (giving it a good 30-second whisking to emulsify). Then whisk in the sour cream and vanilla.

Add the dry ingredients to the wet, and gently fold in with a spatula until halfway combined, then pour in the milk and continue folding everything together until JUST combined.

Assemble: Spread half the batter in your prepared pan. Add half the apple filling mixture on top, in an even layer. Then spread on the remaining batter, and repeat with the remaining apples.

Bake and glaze:  Bake the cake for 45 to 55 minutes. A toothpick inserted into the center should have moist crumbs – not wet batter. 

While the cake is baking, whisk together the powdered sugar, vanilla, and boiled apple cider until smooth. If it's too thick, add the tiniest bit of water or milk.

Let the cake cool in the pan for 15-20 minutes, then release the sides and drizzle on the glaze. Place the cake on a cooling rack to cool for 30-40 more minutes before slicing and serving (this lets the crumb set).

Leftovers can be stored in an airtight container in the fridge for 2-3 days, or room temp for a day.