Prep the pan: Line the bottom of an 8- or 9-inch springform pan with parchment. Lightly grease the sides.
Make the crust: In a bowl, mix almond flour, pistachios, sweetener, and salt.
Stir in melted butter and vanilla until the mixture looks like damp sand.
Press and chill: Press the crust firmly and evenly into the pan. Use the bottom of a measuring cup for a tight pack. Refrigerate while you make the filling.
Whip the cream: In a cold bowl, whip the heavy cream to stiff peaks.
Set aside.
Beat the cream cheese: In another bowl, beat cream cheese until smooth and fluffy. Add sweetener, vanilla, almond extract (if using), salt, and ground pistachios. Beat until creamy with no lumps.
Fold together: Gently fold the whipped cream into the cream cheese mixture in two batches until fully combined and airy.
Fill the crust: Spoon the filling over the chilled crust and smooth the top with an offset spatula.
Chill to set: Cover and refrigerate at least 6 hours, preferably overnight, until firm enough to slice.
Finish and serve: Run a thin knife around the edge, release the springform, and garnish with chopped pistachios or whipped cream.
Slice with a hot, dry knife for clean cuts.