In a stand mixer fitted with the paddle attachment, beat the butter and sugars on medium speed until light and fluffy, about 1 minute. Add the eggs one at a time, then the vanilla.
In a separate bowl, whisk together the flour, baking soda, cinnamon, and salt. Add to the butter and sugar in increments, alternating between the flour and buttermilk. Start and end with the flour.
Fold in the grated apples until combined. Pour into two prepared round 8" cake pans. Bake at 350 degrees Fahrenheit for about 50 minutes, or until a toothpick inserted in the middle comes out clean.
To make the icing, beat the cream cheese and butter together on medium speed until fluffy, about a minute. Slowly add the maple syrup and vanilla, then the powdered sugar in increments. Beat until fluffy and well combined on medium speed, about a minute.
Let the cakes cool down. Once they are at room temperature, flip out of the pans. Using a long, sharp knife, cut the domed top off of one of the cake layers. Spread with half of the cream cheese icing, then place the other cake layer on top. Spread the rest of the cream cheese on top.