Preheat oven to 350F and line baking sheet with parchment paper.
In a large bowl, sift together almond and coconut flours, cream of tartar, baking soda, xanthan gum, and salt.
In a separate bowl, using a mixer, cream together the butter, sweetener, eggs, lemon zest, lemon extract, and lemon juice.
Slowly mix in dry ingredients and combine to form dough.
Roll the individual cookies into 1-1 1/4" balls. Flatten balls slightly for desired shape and bake for 10-12 minutes.
Spread the glaze on the cooled cookies. Let stand until the glaze is set, about 10 minutes.