Preheat oven to 350°F and line a sheet pan with parchment paper.
To make the crumb topping, combine all crumb ingredients in a small bowl. Use a pastry cutter, or two knives, or your hands to cut butter into dry ingredients until mixture is crumbly and all dry ingredients have been incorporated with the butter..
Spread crumbs on the prepared baking pan and bake for 10 minutes, or until crumb mixture is golden brown. Remove from oven and let crumbs cool completely. You can break crumbs into small pieces if necessary.
Store crumbs in a sealed container at room temperature. Crumbs can be made a day or two in advance.
For the cake:
Preheat oven to 350°F. Grease and flour two 8-inch round cake pans.
In a large bowl, whisk together flour, baking powder, cinnamon, nutmeg, ginger, and salt. Add both sugar, eggs, oil, vanilla, and milk. Mix on medium speed with an electric mixer until all ingredients are incorporated, 1 to 2 minutes.
Divide batter evenly between cake pans. Bake for 23-25 minutes or until cakes are golden brown and set in the center. (Test by inserting a toothpick into the center of each cake layer. If it comes out clean, they're done!)
Let cakes cool in pans for about 5 minutes before transferring to a wire rack to cool completely.
To make the frosting + Assembly:
In the bowl of a stand mixer, cream butter and shortening together on medium high speed until smooth. Add vanilla, half of powdered sugar, and 2 tbsp apple butter. Mix on low speed until just combined, then medium high speed until completely combined.
Repeat with second half of powdered sugar.
To assemble the cake, cut domes off of cake layers with a cake saw or serrated knife. Place one cake layer on a cake plate or cake stand.
Pipe a border of frosting around the top edges of the cake. Fill the border with ⅓ - ½ cup of prepared apple butter. You may need more or less depending on how tall the frosting border is.
Sprinkle half of the crumb topping over the apple butter. Place the second cake layer on top.
Spread remaining frosting over the outside of the cake. Pile remaining crumb topping on top.
Store cake covered (or loosely covered) in the refrigerator.