Stir together the granulated sugar and cinnamon in a small bowl. Set aside.
To Make the Cake:
Preheat oven to 350 degrees. Lightly grease a cast iron skillet and set aside. In a large mixing bowl, stir together the flour, cream of tartar, baking soda, and salt.
In another mixing bowl, cream the butter, sugar and eggs until smooth. Add the flour mixture to the liquid mixture slowly until well incorporated.
Scrape the dough into your pan and then use a spatula to smooth.
Sprinkle the cinnamon and sugar topping over the dough.
Bake at 350 degrees for 30-45 minutes.
The cake is done when the edges are lightly browned and the center of the cake is golden in color.
Remove pan from oven and allow to cool on a wire rack for several minutes before cutting cake.
Serve cake topped with ice cream, whipped topping,or whipped cream.