Preheat oven to 350 degrees. Place parchment paper on 2 rimless cookies sheets and set aside.
To the bowl of a stand mixer add the softened butter and sugar. Cream together on high speed for 5 minutes until light and fluffy. Add the egg and egg white and mix until thoroughly combined.
In a large bowl sift together the einkorn flour, cream of tartar, baking soda, salt and 1 tsp cinnamon. Mix together until combined then fold into the wet ingredients. Mix only until no dry spots are visible. Cover with plastic wrap and let rest in the refrigerator for 1 hour. Einkorn takes more time to absorb liquids than conventional flour and needs a resting period. After the dough has chilled, divide into walnut-sized balls—you should get about 2 dozen.
Mix the remaining 2 Tbsp cinnamon and ½ tsp sugar in a small bowl then roll each of the dough balls in the mixture to coat evenly. Place on the baking sheet approximately 2" apart. Press each ball flat with the bottom of a drinking glass or coffee cup until ½" thick. If it begins to stick, just dip the bottom of the glass in the cinnamon sugar.
Bake 8–10 minutes until they have a crackled appearance and are lightly browned around the edges. Remove from oven, transfer to a cooling rack and enjoy!