Mix the melted butter, sugar, and brown sugar together until smooth. Add one whole egg, one egg yolk, and the vanilla extract. Stir until smooth.
In a separate bowl, mix flour, cream of tartar, salt, baking soda, and 3/4 teaspoon ground cinnamon.
Fold the dry ingredients into the wet ingredients. Don't overmix the dough. Cover with cling wrap and chill for one hour.
Preheat the oven to 325 degrees F. In a small bowl stir together the white sugar and cinnamon.
Remove the dough and roll into balls, about walnut sized. Roll the balls of dough in the cinnamon-sugar mixture.
Bake for 9-11 minutes. Allow cookies to sit on cookie sheet for two minutes before moving them to a cooling rack.
Adapted from Chelsea's Messy Apron.