Preheat oven to 190 C (375°F) and set middle rack in the middle.
Line a baking tray with parchment paper.
Combine the flour, salt, cinnamon, baking soda and cream of tartar in a bowl and using a whisk mix together.
In a mixing bowl with a paddle attachment ( you can also use a hand mixer) add the butter, shortening and 300 grams of sugar and mix on medium speed scraping down the sides of the bowl occasionally until mixture is smooth and fluffy about 4-5 minutes.
Mix in the eggs, one at a time and continue to mix until well combined about 45 seconds.
Lower to reduce the mixing speed to slow setting and add the flour mixture mixing for about 40 seconds or until the snickerdoodle cookie dough starts to form.
In a separate bowl add the 400 grams sugar and 23 grams of cinnamon and mix together with a whisk until well combined.
Scoop 2 tablespoons of cookie dough and roll them into a ball and coat with the cinnamon sugar mixing and place into baking tray. Repeat spacing each cookie about 2 inches apart from each other.
Baking one tray at a time place the baking tray into the preheated and bake for 10-12 minutes or until the edges are golden brown.
Remove from oven and cool cookies on a wire rack. Repeat baking the rest of the cookies.
This recipe will yield about 24 cookies. Depending on the size of your baking tray, you will have to bake 2 or 3 times given that you can fit 8-12 cookies per tray. You have the option of freezing the rest of the cookie dough and bake at a later date. Just shape them and place in a freezer friendly zip lock bag. The cookie dough with freeze well up to a month.
To bake your Snickerdoodle raw cookie dough, preheat your oven to 165 C (330°F) and baking from frozen state for 15-18 minutes.