In a mixing bowl, combine almond flour, melted unsalted butter, granulated erythritol, salt, and lemon zest until well blended. Press this mixture firmly into the bottom of an 8-inch springform pan to form a solid crust. Chill the crust in the refrigerator for 30 minutes.

In a large mixing bowl, whip the heavy cream with half of the monk fruit sweetener using an electric mixer until soft peaks form, about 3-5 minutes. In another bowl, blend together the whole milk ricotta, mascarpone cheese, remaining monk fruit, lemon juice, vanilla extract, and a pinch of salt until smooth and creamy.

In a small saucepan, heat ¼ cup of water over low heat and sprinkle the powdered gelatin over the surface. Stir continuously until the gelatin dissolves completely, about 1-2 minutes. Remove from heat and let cool slightly.

Slowly drizzle the cooled gelatin mixture into the ricotta and mascarpone blend while mixing gently. Fold in the whipped cream carefully to keep the filling light.

Pour the creamy filling over the chilled crust and smooth the top. Cover with plastic wrap and refrigerate for 2-4 hours until set.