In a medium bowl, combine the almond flour, melted butter, and granular erythritol and stir until the mixture resembles damp sand and holds together when pressed.

Transfer the crust mixture to a 9-inch pie dish and press it firmly and evenly into the bottom and slightly up the sides using your fingers or the bottom of a measuring cup.

Place the crust in the refrigerator to chill and firm for 15 minutes.

While the crust chills, add the softened cream cheese to a mixing bowl and beat with a hand mixer or stand mixer until completely smooth.

Add the powdered erythritol, fresh lemon juice, and lemon zest to the cream cheese and beat until the mixture is smooth and fully combined, scraping down the sides of the bowl as needed.

In a separate bowl, whip the heavy cream with a mixer on medium-high speed until soft peaks form.

Gently fold the whipped cream into the lemon cream cheese mixture using a spatula until just combined and no streaks remain.

Pour the lemon filling over the chilled almond flour crust and smooth the top with a spatula.

Refrigerate the pie for at least 4 hours, or until fully set and firm enough to slice cleanly.

Slice with a sharp knife and serve chilled.