Preheat oven to 350°F. Line an 8x8 inch baking pan with parchment paper, leaving overhang on two sides.
Mix the almond flour, powdered erythritol, melted butter, and sea salt together until evenly combined. Press the mixture firmly and evenly into the bottom of the prepared pan using the back of a measuring cup. Bake for 12 to 14 minutes until the edges are lightly golden. Remove and reduce oven temperature to 325°F.
While the crust bakes, whisk together the eggs, fresh lemon juice, lemon zest, and powdered erythritol until well combined and smooth. Sift in the coconut flour and whisk until no lumps remain.
Pour the lemon filling over the hot crust. Return the pan to the oven and bake at 325°F for 18 to 22 minutes, until the filling is set and no longer jiggles in the center when gently nudged.
Let cool completely at room temperature, then refrigerate for at least 2 hours until fully chilled and firm. Lift out using the parchment overhang, dust generously with powdered erythritol, and cut into 12 bars.
