Mix: butter, 1 1/2 cup almond flour, 1/4 cup erythritol, and a pinch of salt. Press evenly into an 8×8″ parchment paper-lined baking dish. Bake for 20 minutes at 350 degrees F. Then, let cool for 10 minutes.
Into a bowl, zest one of the lemons, then juice all 3 lemons, add the eggs, 1/2 cup erythritol, stevia, 3/4 cup almond flour & pinch of salt and sour cream. Combine to make filling.
Pour the filling onto the crust & bake for 25 minutes.
Serve with lemon slices and a sprinkle of erythritol.