Preheat oven to 350°F.
Prepare three 8" cake pans by lightly greasing the sides of the pans and then dusting with flour, then line the bottom of the pans with parchment paper.
In a medium bowl, combine flour, baking powder, salt and spices. Whisk, then set aside.
In the bowl of an electric mixer, beat butter until smooth. While mixing, slowly add sugar and continue to beat until the butter and sugar are well combined and the mixture is light and fluffy. Don't skimp on the mixing at this stage.
While mixing, add the eggs one at a time, blending at least 10-20 seconds between each additional egg. Mixing well to incorporate some air is important in this step.
Add vanilla and oil, and blend well to combine.
Add sour cream and blend.
Reduce the mixer speed to low, and pour in about half of the milk, then half of the flour mixture. Repeat with milk and flour. Blend just until all ingredients are well combined. Stop mixer and scrap down the sides of the bowl, and stir (just a couple times) by hand just to make sure all ingredients are well blended.
Add 1 1/2 cups of the cooked spiced apples (from recipe above) to the bowl and use a large spatula to fold the apples into the batter. Stir just until evenly combined. (Reserve the remaining spiced apples for when the baked cake is being assembled)
Divided batter evenly into prepared pans.
Bake in preheated 350°F. oven for 22-28 minutes, or until the cake has a slight dome and a toothpick inserted in the center comes out clean, or with a few moist crumbs, but no wet batter.
Cool cakes in pans for 5-10 minutes, then carefully remove and continue cooling on a wire cooling rack (leave the parchment on the bottoms at this point). Once cakes are mostly cool, wrap well in plastic wrap and place cakes in the freezer. This will help keep them moist as they fully cool, and will make them easy to handle (stack and frost) when you're assembling the cake.