Preheat oven to 350 degrees. Oil three 9-inch cake pans, and line the bottoms with a circle of parchment paper.
Combine the flour, baking powder, baking soda, cinnamon, ginger and salt in a large bowl. In a smaller bowl whisk together the milk, applesauce, vinegar, oil, vanilla, sugar and brown sugar.
Pour the wet mixture into the dry and whisk briefly, just until thoroughly mixed. Divide the batter evenly among the three pans, and bake 25 to 30 minutes, or until the tops bounce back when lightly pressed. You can also use a toothpick inserted in the center to test for crumbs. Allow to cool in the pans for about 10 minutes then transfer cakes to cooling racks. Cool completely before frosting. If making in advance, wrap each layer individually in plastic wrap and refrigerate overnight.
Make the filling:
In a medium saucepan over medium heat, cook the apples, brown sugar and maple syrup until the apples have softened and the mixture has thickened, about 10 to 15 minutes.
In a mug or small bowl whisk the corn starch into the bourbon and add to the pan. Cook for another 3 to 5 minutes or until all the liquid has evaporated and the filling is jam-like. Transfer the filling to a bowl to cool completely. If making in advance, store the filling in an airtight container in the refrigerator. The filling should be no warmer than room temperature when assembling the cake.
Make the buttercream:
Using a handheld or stand mixer, cream the butter until light and fluffy, about 5 minutes. Add the sifted powdered sugar 1 cup at a time, beating on low speed between additions and scraping down the sides of the bowl as needed. Taste for sweetness, and add the final ½ cup of sugar if desired. Add the cinnamon and vanilla, and beat on medium/high speed until fully incorporated and smooth. If making in advance, store the frosting in an airtight container in the refrigerator.
Assemble the cake:
Place one cake layer on a serving plate or cake stand. Using an offset spatula spread a thin layer of frosting on the top and sides of the cake. Spoon about half of the bourbon-apple filling onto the frosting and spread in an even layer.
Place the 2nd cake layer. Repeat the process of spreading the frosting and apple filling. If your cakes are a bit domed and you want the filling to peek out through the side gaps (as pictured) frost the sides carefully to avoid getting frosting on the apple filling.
Place the 3rd cake layer and frost the top and sides.
Core and slice the apple, coating each slice in lemon juice to prevent browning. Decorate the cake with apple slices, nuts, and a sprinkle of cinnamon. Serve and enjoy!
Store leftover cake in an airtight container in the refrigerator. As with all cakes, it will begin to dry out once it's sliced.
Vegan Apple Layer Cake https://myquietkitchen.com/apple-layer-cake-with-bourbon-apple-filling-and-cinnamon-buttercream/