Preheat your oven to 350°F. Line an 8x8 inch baking pan with parchment paper, leaving some overhang on the sides for easy removal.
In a medium bowl, mix together the almond flour, powdered sweetener, melted butter, and salt until a crumbly dough forms.
Press the crust mixture evenly into the bottom of the prepared pan. Use the bottom of a flat glass to compact it firmly.
Bake the crust for 12 to 14 minutes until lightly golden around the edges. Remove from the oven and let cool for 5 minutes.
While the crust cools, whisk together the eggs, powdered sweetener, lemon juice, lemon zest, and almond flour in a bowl until smooth and combined.
Pour the lemon filling over the pre-baked crust.
Return the pan to the oven and bake for 15 to 18 minutes, until the filling is just set with a slight jiggle in the center.
Remove from the oven and allow to cool completely at room temperature, then refrigerate for at least 2 hours before slicing.
Slice into 12 bars and dust with powdered erythritol before serving if desired.