Preheat oven to 350°F. Line an 8x8-inch baking pan with parchment paper, leaving an overhang on two sides for easy removal.
In a bowl, mix almond flour, melted butter, powdered erythritol, and salt until evenly combined. Press the mixture firmly and evenly into the bottom of the prepared pan.
Bake the crust for 12-15 minutes until the edges are lightly golden. Remove from the oven but leave it on.
While the crust bakes, whisk together eggs, lemon juice, powdered erythritol, coconut flour, and lemon zest until smooth and no lumps remain.
Pour the lemon filling over the hot crust. Return to the oven and bake for 18-20 minutes until the filling is set and no longer jiggles in the center.
Let cool completely at room temperature, then refrigerate for at least 2 hours until firm. Dust with extra powdered erythritol before slicing into 12 bars.
