Heat the oven: Preheat to 350°F (175°C). Lightly grease a 9-inch pie plate.
Make the crust: In a bowl, stir almond flour, powdered sweetener, and salt.
Add melted butter and vanilla. Mix until it looks like damp sand and clumps when pressed.
Press and bake: Press the mixture evenly into the pie plate, going up the sides. Prick the base a few times with a fork.
Bake 10–12 minutes, until lightly golden at the edges. Cool completely.
Bloom the gelatin: Sprinkle gelatin over the cold water in a small bowl. Let sit 5 minutes to hydrate.
Cook the lemon base: In a saucepan, whisk lemon juice, zest, powdered sweetener, egg yolks, and salt.
Cook over medium-low heat, stirring constantly, until it thickens slightly and reaches a gentle simmer, 4–6 minutes. Do not boil hard.
Add gelatin and vanilla: Remove the pan from heat. Stir in the bloomed gelatin until fully dissolved, then add vanilla.
Let the mixture cool to just warm, about 15 minutes, stirring occasionally.
Whip the dairy: In a large bowl, beat the cream cheese until smooth. In a separate bowl, whip 1 1/4 cups cold heavy cream to soft peaks.
Combine: Beat the warm lemon mixture into the cream cheese until silky. Gently fold in the whipped cream in two additions, keeping the mixture airy.
Fill the crust: Spoon the lemon cream into the cooled crust.
Smooth the top with a spatula.
Chill: Refrigerate at least 4 hours, or until set. Overnight is ideal for clean slices and the best texture.
Optional topping: Whip 1/2 cup cream with powdered sweetener to soft peaks. Spread or pipe over the chilled pie.
Garnish with thin lemon slices or a dusting of zest.
Serve: Use a sharp knife wiped clean between cuts. Enjoy cold.