Melt butter in a sauce pan and pour in your granualted sweetener. Mix until combined
Add in your lemon juice and lemon extract. If it's still hot move on to fixing your dry ingredients before you add your eggs. You want it to cool a bit and not be hot
Add eggs if cool, if not go to next step then come back
combine dry ingredients. Almond flour, coconut flour, baking powder, and baking soda.
Zest half a lemon in dry ingredients, then mix the powders and zest up with a spoon or whisk
combine dry and wet, then pour into a 9 inch round cake pan