In a medium bowl, stir together the almond flour, melted butter, erythritol, and salt until well combined. Press the mixture firmly into the bottom of an 8-inch or 9-inch springform pan. Place the pan in the refrigerator while you prepare the filling.
In a large bowl, beat the cream cheese with an electric mixer on medium speed until smooth and fluffy, about 2 minutes. Add the powdered erythritol, vanilla extract, and lemon juice. Beat until fully incorporated.
In a separate bowl, whip the heavy cream with the electric mixer on high speed until stiff peaks form, about 3 to 4 minutes.
Gently fold the whipped cream into the cream cheese mixture in two additions, using a spatula. Fold carefully to keep the filling light and airy.
Spoon the filling over the chilled crust and smooth the top with a spatula.
Cover the pan with plastic wrap and refrigerate for at least 6 hours or overnight, until the cheesecake is firm and slices cleanly.
Run a thin spatula around the edges before releasing the springform ring. Slice and serve chilled.