Preheat the oven to 350 degrees F. Line 2 large baking sheets with a Silpat baking mat or parchment paper and set aside.

In a medium bowl, whisk together flour, cream of tartar, baking soda, and salt. Set aside.

In the bowl of a stand mixer, beat the butter and sugar together until light and creamy, about 2 minutes. Scrape down the sides of the bowl with a spatula, if necessary.

Add the eggs and vanilla extract and beat until combined.

Turn the mixer off and add all the dry ingredients. Mix on low until just combined. Don't over mix.

Stir in the toffee bits.

Roll the cookie dough into balls, about 2 tablespoons of dough per cookie.

In a small bowl, combine the sugar and cinnamon. Roll the cookie balls into the cinnamon sugar mixture, making sure each cookie ball is generously coated.

Place the cookie dough balls onto the prepared baking sheet, about 2 inches apart. Bake for 8 to 10 minutes or until cookies are set around the edges but still soft in the center. Check early to be safe, you don’t want to over bake. The cookies will set up after they cool.

Remove the baking sheet from the oven and let the cookies cool on the sheet for 5 minutes. Transfer to a wire cooling rack and cool completely.