Cook cinnamon stick in water for about 5 minutes to get cinnamon tea. Let cool completely.
Put flour, shortening and baking powder in a food processor (you can do this by hand, too). Mix or pulse until you get coarse crumbs. Add cooled cinnamon tea little by little, while mixing all the time, until you get smooth dough.
Bake Pan de Polvo cookies in preheated 350 F (175 C) oven for about 15 minutes.
Combine granulated sugar and ground cinnamon in a bowl. Roll Mexican shortbread cookies in this mixture while they are still hot.