First, start by preheating the oven to 375°F (190°C) and placing the rack in the middle. Then, line a baking sheet with non-stick baking paper.
Start by combining the flour, baking powder, and baking soda in a medium-sized bowl. Set the dry ingredients aside. Then, combine the sugar and salted butter together and cream them until they become light and fluffy. Beat this mixture for about 3 minutes. Then, add the egg and mix it well. Finally, beta in the vanilla extract and ground cinnamon. Now, add the flour mixture to the wet ingredients and mix them until a uniform dough just comes together.
First, combine the ingredients for the snickerdoodle cookie topping to make cinnamon sugar. Set it aside in a medium bowl. Now, divide the cookie dough into 20 equal-sized balls. Then, neatly roll them into smooth balls. Dip each ball into the cinnamon-sugar coating and place them on the baking sheet, about 3 inches apart. Continue doing so until all of the cookies have been coated.
Place the cookies inside of the preheated oven on the middle rack. Then, allow them to bake for about 12 minutes, or until the center is gooey but the edges are set. Then, remove the snickerdoodle cookies from the oven and allow them to cool on a wire rack for at least 20 minutes. They should be firm once they have set.