Preheat the oven to 375 F/190 C.
In a mixing bowl, cream together the butter and sugar until well combined, about 1-2 minutes.
Scrape down the bowl and add the egg and vanilla. Mix to completely combine. Scrape down the bowl again.
Add the flour, baking soda, salt, and cream of tartar and mix on low until combined. Remove from the mixer and add the cooled cinnamon crumb. Fold in the crumb with a spatula until just combined.
Scoop the dough onto a lined baking tray with a large (¼ cup) cookie scoop and press extra cinnamon crumbs onto the tops of each ball. Place the tray in the fridge to chill for 30-40 minutes.
Bake for 12-13 minutes, or until the edges are JUST starting to turn golden. Let the tray cool completely on a wire rack before enjoying.