Beat the 1 cup of butter in a large mixing bowl for 30 seconds. Add the 1 1/2 cups of sugar and 1/2 cup pumpkin to the bowl. Beat until the ingredients are combined.Add the vanilla, cream of tartar, baking soda and salt to the bowl. Beat in as much of the flour as you can with the mixer. Stir in the remaining flour with a wooden spoon. Cover the bowl with plastic wrap and refrigerate the dough for 1 hour.Place 1/2 cup sugar and 1 Tablespoon cinnamon in a small bowl, stir the ingredients together to combine them. Drop cookie dough into the cinnamon sugar mixture, rolling the dough in the mixture to coat them. Place cookies 2 inches apart on a parchment paper lined cookie sheets, 2 inches apart.Bake in a 350 degree preheated oven for about 10 minutes or until edges are golden brown. Remove the cookies from the baking sheets to a wire rack to cool.