Preheat oven to 300℉. Grease three 8" round cake pans. Set aside.
In a medium bowl, mix flour, baking soda, and salt. Set aside.
In a large bowl/stand mixer, cream ¾ cup butter and the sugar until light and fluffy. Beat in the eggs one at a time, then stir in 1 tablespoon vanilla, pumpkin puree, and vegetable oil. Beat in the flour mixture alternately with the milk.
Divide batter evenly into prepared pans. Bake for 35-40 minutes, or until a toothpick comes out clean. Remove pans from oven and immediately place in freezer for 45 minutes. (This keeps the cake moist by immediately stopping the baking.)
For the Frosting
In a large bowl, cream the other ¾ cup butter and the cream cheese until smooth. Beat in maple syrup, 2 teaspoons vanilla, and cinnamon. Add powdered sugar and beat on low speed until combined, then on high until frosting is smooth.
Assemble the 3 layers with a thick layer of frosting between each layer. Apply a thin crumb coat on the top and sides. Pop back in the freezer to harden the crumb coat for about 10 minutes.
Apply one final thick and even layer around the outside of the cake. Store in the fridge until ready to serve.