Step 1: Preheat your oven to 350°F (175°C) and line two large baking sheets with parchment paper or silicone mats.
Step 2: In a large bowl, cream together the softened butter, granulated sugar, and brown sugar until the mixture is light and fluffy.
Step 3: Beat in the eggs one at a time, then stir in the vanilla extract until well combined.
Step 4: In a separate medium bowl, whisk together the flour, baking soda, cream of tartar, salt, and 1 tablespoon of cinnamon.
Step 5: Gradually add the dry ingredients to the wet ingredients, mixing just until combined. Do not overmix.
Step 6: In a small bowl, prepare the coating by mixing 1/4 cup sugar and 1 tablespoon cinnamon.
Step 7: Scoop about 1.5 tablespoons of dough, roll into a ball, and roll thoroughly in the cinnamon-sugar mixture.
Step 8: Place dough balls 2 inches apart on the prepared baking sheets and bake for 9-11 minutes, or until the edges are just set but the centers still look slightly soft.
Step 9: Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.