Preheat oven to 350 degrees and line a baking pan with parchment paper or a non-stick baking mat.

In a bowl, mix together dry ingredients - flour, baking powder, salt, and 1 teaspoon cinnamon; set aside.

In a mixer fitted with a paddle attachment (hand-held mixers work too), cream together butter, granulated sugar and brown sugar. Next add vanilla extract and eggs one at a time, mixing after each. Scrape down sides of the bowl as necessary.

With mixer on low-speed, gradually add the bowl of dry ingredients and mix until incorporated, do not over-mix though.

Cover bowl with plastic wrap and place in freezer for 15 minutes to chill. Can also place in the refrigerator if you plan on making the cookies later. You do not have to chill the dough, but it is much easier to roll into a ball if it is chilled a little.

To make the cinnamon sugar, mix sugar and cinnamon in a bowl.

Measure about 1½ tablespoons of dough, roll into a ball and then roll in cinnamon sugar and place on prepared cookie sheet. Bake for 8-10 minutes (mine baked for 9). I've had a few comments about them not being fully baked at 10 minutes. Every oven is different so it may take up to 20 minutes for your cookies to fully bake through. I suggest starting at 10 minutes and then watch them from there. However, you do not want to over bake as snickerdoodle cookies are known for their soft and chewy texture. Cookies will look puffy when they are done, remove from oven and let cool slightly on baking sheet then move to cookie sheet to cool completely. Cookies will flatten a little as they cool.