Whisk together the flour, baking soda, cream of tartar, cinnamon, and salt. Set aside.
Using an electric mixer on medium speed, beat the butter, sugar, and brown sugar until light and fluffy. Add the eggs, one at a time, mixing well after each addition. Mix in the vanilla.
Reduce mixer speed to low. Gradually add the flour mixture, mixing until a few streaks of flour remain. Stir in the toffee bits and pecans until the dough is just combined.
Cover and chill 1 hour.
To make the cinnamon-sugar and assemble the cookies:
Preheat oven to 350°F (175°C). Line baking sheets with silicone liners or parchment paper.
Mix the sugar and cinnamon in a small bowl until combined.
Using about 1 & 1/2 tablespoons of dough at a time, shape the dough into balls. Roll each dough ball in cinnamon-sugar.
Place the cookies on the prepared pans, leaving about 2 inches between cookies. Bake 10 to 12 minutes, or until the edges are lightly browned.
Cool the cookies on the pan on a wire rack for 5 minutes. Then, transfer the cookies to a wire rack to cool completely.