Preheat oven to 350 degrees and line a 9" springform pan with buttered parchment paper. Combine butter and gram cracker crumbs, press into the bottom of the pan, slightly working the crumbs up the side a bit. Set aside.

With a mixer, beat cream cheese and sweetened condensed milk until smooth and lump-free (about 3-4 minutes on low), add eggs and vanilla and mix for another 30-45 seconds - until eggs are fully incorporated. Reserve 1 cup of the batter for the top layer, pour the remaining batter over the prepared graham cracker crust. Spread the batter out evenly with a spatula. Combine the reserved batter with the pumpkin puree and cinnamon. Gently pour the pumpkin layer atop in a circle evenly distribute the top layer - carefully spread out the pumpkin to cover the top.

Bake for 45-50 minutes, turning the pan 180º at about the 23 minute mark. The cheesecake will still have a little giggle to it, yet be firm on top when finished.

On a baker's rack, cool in the pan for 30 minutes, loosen the sides of the cake with a knife and remove ring of the pan, continue to cool at room temperature for an additional 30 minutes. Chill for at least 5 hours before serving.