Preheat your oven to 350°F (175°C) and line a 9x13-inch baking pan with parchment paper, leaving overhang on the sides for easy removal. Allow cream cheese to soften at room temperature for at least 30 minutes.
Combine graham cracker crumbs, melted butter, sugar, and cinnamon in a bowl until the mixture resembles wet sand. Press firmly into the bottom of your prepared pan, creating an even layer. Use the flat bottom of a measuring cup to apply pressure for a firm crust.
Bake the crust for 8-10 minutes until lightly golden. Remove from the oven and allow to cool slightly while preparing the filling layers.
In a large bowl, beat softened cream cheese and sugar until light and fluffy, about 2-3 minutes. Add eggs one at a time, then vanilla, beating just until incorporated. Be careful not to overmix after adding eggs.
In a separate bowl, whisk together pumpkin puree, eggs, sugar, heavy cream, pumpkin pie spice, salt, cinnamon, and nutmeg until silky smooth.
Pour the cream cheese mixture over the cooled crust, spreading evenly with an offset spatula. Gently spoon the pumpkin mixture on top, taking care not to disturb the cream cheese layer. For the cleanest layers, pour the pumpkin mixture over the back of a large spoon.
Bake for 45-50 minutes, or until the center is almost set but still slightly jiggly. The edges will be slightly puffed and center should wobble like set gelatin when gently shaken.
Allow the bars to cool completely at room temperature (about 1 hour), then refrigerate for at least 2 hours, preferably overnight.
Cut into bars using a large sharp knife dipped in hot water and wiped clean between each cut for perfect presentation.