Preheat your oven to 350°F (175°C). This ensures that your cookies bake evenly.
In a large mixing bowl, combine the softened butter and 1 cup of sugar. Using an electric mixer, beat them together until light and fluffy, about 2-3 minutes.
Crack the egg into the bowl and add the vanilla extract. Continue mixing until well combined.
In another bowl, whisk together the all-purpose flour, baking soda, cream of tartar, and ground cinnamon. This step ensures that all the dry ingredients are evenly distributed.
Gradually add the dry ingredients to the butter mixture. Mix until just combined, being careful not to overmix.
In a small bowl, combine the remaining 2 tablespoons of sugar with 1 teaspoon of ground cinnamon. This will be used to roll your cookie dough balls.
Using a cookie scoop or a spoon, portion out the dough and roll it into balls. Roll each ball in the cinnamon sugar mixture until fully coated.
Place the coated dough balls on the ungreased baking sheet, leaving space between each one for spreading. Bake for 10-12 minutes, or until the edges are lightly golden.
Remove the cookies from the oven and let them cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely. Enjoy your delicious Snickerdoodles with a glass of milk or your favorite beverage!