Preheat the oven: Preheat your oven to 375°F and line two baking sheets with parchment paper.

Cream butter and sugar: In a large bowl, beat the softened butter and 1 1/2 cups sugar together until pale and fluffy, about 2 minutes.

Add eggs and vanilla: Beat in the eggs one at a time, then add the vanilla extract, mixing until the batter looks smooth and glossy.

Whisk dry ingredients: In a separate bowl, whisk together the flour, cream of tartar, baking soda, and salt until evenly combined.

Combine wet and dry: Add the dry ingredients to the wet mixture in two batches, mixing just until no streaks of flour remain.

Make the coating: In a small bowl, stir together the 2 tablespoons sugar and cinnamon for rolling the dough balls.

Scoop the dough: Scoop the dough into 1.5-inch balls using a cookie scoop or tablespoon, rolling each one between your palms until smooth.

Roll in cinnamon sugar: Roll each dough ball in the cinnamon sugar mixture, pressing gently so the coating sticks in an even layer.

Arrange on baking sheets: Place the coated dough balls about 2 inches apart on the prepared baking sheets to allow room for spreading.

Bake until cracked: Bake for 8 to 10 minutes, until the edges are set and the tops have puffed and cracked, with centers that still look slightly soft.

Cool on the pan: Let the cookies cool on the baking sheet for 5 minutes; they will firm up as they rest.

Transfer and finish cooling: Move the cookies to a wire rack to cool completely before storing in an airtight container.