01 - Preheat oven to 190°C. Line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together flour, cream of tartar, baking soda, and salt.
03 - In a large bowl, beat softened butter and 300 g sugar until light and fluffy. Add eggs one at a time, mixing well after each addition.
04 - Gradually mix the dry ingredients into the wet mixture to form a soft dough.
05 - In a small bowl, combine 50 g sugar and ground cinnamon for coating.
06 - Roll dough into 2.5 cm balls and coat each ball evenly in the cinnamon-sugar mixture.
07 - Place coated dough balls 5 cm apart on prepared baking sheets.
08 - Bake in the preheated oven for 9 to 11 minutes, until edges are set but centers remain soft.
09 - Allow cookies to cool on the baking sheet for 2 minutes, then transfer to a wire rack to cool completely.