In a medium sized mixing bowl, combine the cashew butter, coconut oil, egg, and vanilla. Stir to mix well.
Into the cashew butter mixture, add the sugar, baking soda, sea salt, cinnamon, and cream of tartar. Stir to mix these ingredients in.
Add the oat flour and arrowroot flour, and stir until it forms a sticky dough. Refrigerate the cookie dough for about 30 minutes. If you need to refrigerate the dough overnight, cover it so that it does not dry out.
Preheat the oven to 350º F.
Mix the coarse sugar and cinnamon together in a small bowl.
Use a 1 tablespoon measuring spoon to scoop the dough out. This measurement will yield 24 cookies. The cookies rise and spread while baking so they end of being nice sized cookies. Form the cookie dough into a ball, and roll it in the cinnamon and sugar mixture.
Add the cookie dough balls to a baking try with room around each to allow for spreading. Use a fork to press down the cookie dough balls into a flattened round shape. If you prefer pillowy, thick cookies, skip this step and just bake them as balls. You can see the difference in the photos above between the pillowy cookies and the flattened cookies.
Bake for 9 minutes.
The cookies will be very soft when they come out of the oven. Allow the cookie sheet to completely cool, and the refrigerate or freeze the cookies on the cookie sheet to fully chill. Store the cookies in the refrigerator or the freezer and enjoy them chilled. I think the cookies have the best chewy texture when frozen!