Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper.

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

In a large bowl, beat the softened butter with the granulated and brown sugars until smooth and slightly fluffy, about 2–3 minutes.

Add the eggs one at a time, beating briefly after each, then stir in the vanilla until combined.

Gradually add the dry ingredients and mix until just combined — don’t overmix. The dough should be soft but not sticky.

In a small bowl, combine 2 tablespoons granulated sugar with 1 tablespoon ground cinnamon.

Scoop or roll dough into 1 to 1½ tablespoon-sized balls. Roll each ball in the cinnamon-sugar to coat.

Place the coated dough balls on the prepared baking sheets, spacing them about 2 inches apart.

Bake for 8–10 minutes until the edges are lightly golden and the centers still look slightly soft.

Let cookies cool on the baking sheet for 2–3 minutes, then transfer to a wire rack to cool completely.