Prep the oven: Preheat to 350°F (175°C). Place a rack in the lower-middle position.
Lightly grease a 9-inch pie dish.
Make the crust: In a bowl, whisk almond flour, sweetener, salt, and cinnamon. Stir in melted butter, egg, and vanilla until the dough is moist and clumps when pressed.
Form the crust: Press the dough evenly into the bottom and up the sides of the pie dish. Aim for an even thickness with no cracks.
Use the back of a spoon or a flat-bottomed cup to smooth.
Par-bake: Bake the crust for 10–12 minutes until just set and lightly golden at the edges. Remove and let cool 10 minutes. Lower oven to 325°F (165°C).
Mix the filling: In a large bowl, whisk pumpkin, sweetener, spices, and salt until smooth.
Whisk in eggs one at a time, then add heavy cream and vanilla. Mix until velvety with no streaks.
Fill and bake: Pour the filling into the warm crust. Tap the dish gently to release air bubbles.
Bake at 325°F for 45–55 minutes, until the edges are set and the center still has a slight jiggle.
Cool completely: Set the pie on a rack and cool to room temperature. This helps it set cleanly.
Chill: Cover and refrigerate at least 4 hours, preferably overnight, for the best texture and flavor.
Serve: Slice with a warm, clean knife. Top with whipped cream if you like and a pinch of cinnamon.