Preheat the oven to 350 F. In a medium bowl, whisk together flour, salt, baking soda, and cream of tartar. In a large bowl, combine butter with sugar until fluffy.
Add in the egg and vanilla extract, and mix until smooth. Add in the flour mixture, and mix until it is fully combined. Place the sugar and cinnamon into a shallow dish.
Roll the cookie dough into balls, and roll each ball into the cinnamon sugar mixture. Place the cookies onto a large ungreased baking sheet. Bake for 10-12 minutes.
Remove from the oven, and decorate each cookie with the pretzels, chocolate chips and m&ms.
