Preheat oven to 350 F. And a small bowl mix together the melted butter, brown sugar, flour, and chopped pecans. Grease a 9 inch cake pan well with oil and line the bottom with parchment paper. Press the pecan mixture into the bottom of the pan with the base of a measuring cup or with your hands. Make sure it is packed down tightly. set aside.
In a large mixing bowl beat together the butter, sugar, and brown sugar until creamy. Add the apple cider, egg, and vanilla extract and continue to mix well.
Fold in the flour, baking powder, cinnamon, nutmeg, and sea salt with a rubber spatula. Only fold until the flour is 90% incorporated. Add the apple pieces and fold into the batter.
Pour the cake batter on top of the pecan base in the cake pan. Use a knife or spatula to even out the batter. Bake in the oven for 40 - 50 minutes until you can insert a toothpick into the center and it comes out clean. Let the cake cool completely before assembling.
Once the cake is cool make the icing by mixing together the cream cheese, apple cider, and maple syrup with a spoon until smooth. Add at the powdered sugar and cinnamon and continue to mix until well incorporated. You want the icing to be on the thicker side so that you get a nice coat of icing on top of the cake, however, add a splash of milk if needed to send it out.
For the icing over the cooled cake. Use an offset spatula if needed to spread the icing just up to the edges of the cake. Let the icing set while you make the cinnamon apples.
Place the thinly sliced apples, butter, and cinnamon in a skillet. Heat on the stove over medium heat until the apples are soft. Stir occasionally to prevent burning. Let the apples cool down before piling them on top of the cake.
When ready to serve use a sharp knife to cut the cake into pieces and enjoy!
Store leftover cake in an airtight container out on the counter for 2 - 3 days.