Heat oven to 350F, then line a baking sheet with parchment paper. In a large mixing bowl, combine almond flour, coconut flour, psyllium husk fiber, baking powder and baking soda. Whisk in poppy seeds until well combined.

Cut butter into the dry ingredients with a fork, pastry cutter, or your hands until a dough forms.

In a separate bowl, whisk together the eggs and sweetener until frothy.

Zest lemon onto a plate and add the sprinkling erythritol. Using a fork, mash the sugar and zest together to combine and set aside to dry.

Cut the lemon in half and squeeze the juice into the egg mixture. While being careful not to get any seeds in it, any pulp that may get mixed in is okay and actually provides a nice texture.

Pour the egg mix into the dry mix and stir well to form a dough.

Place the wet dough onto the prepared parchment in a dome shape.

Gently score the wet dough with a knife to form even triangles, then bake for 20 minutes.

Remove from oven, cut along the scored lines into even triangles and separate each slice. Sprinkle with lemon sugar and bake for 10 more minutes.