Preheat the oven: Set to 350°F.
Make the crust: In a bowl, mix almond flour, melted butter, erythritol, cinnamon, and salt until crumbly dough forms.
Form the crust: Press the dough into a 9-inch pie pan, covering the bottom and sides evenly.
Prebake: Bake for 10 minutes, then remove and set aside.
Prepare the filling: In a large bowl, whisk together pumpkin puree, sweetener, eggs, heavy cream, vanilla, and spices until smooth.
Fill and bake: Pour the filling into the crust. Bake 40–50 minutes, or until the center is mostly set but still slightly wobbly.
Cool: Let the pie cool at room temperature, then chill at least 3 hours before slicing.
Serve: Top with sugar-free whipped cream and a sprinkle of cinnamon.