Whisk the dry ingredients. In a medium bowl, whisk together flour, cream of tartar, baking soda, and salt. This ensures even rise and prevents clumps.

Cream the butter and sugars. In a large mixing bowl, beat the butter, granulated sugar, and brown sugar on medium speed for 2–3 minutes until light and fluffy. Proper creaming traps air and helps the cookies puff in the oven.

Add eggs and vanilla. Beat in the eggs one at a time, then add the vanilla. Mix until smooth and glossy, scraping down the bowl as needed.

Combine wet and dry. Add the dry ingredients to the wet mixture. Mix on low just until combined and no dry streaks remain. Don’t overmix or you’ll lose softness.

Chill the dough. Cover the bowl and refrigerate for at least 45–60 minutes, or up to 24 hours. Chilled dough bakes thicker and keeps the centers tender.

Preheat and prep. Heat the oven to 350°F (175°C). Line baking sheets with parchment paper for even browning and easy cleanup.

Make the cinnamon-sugar. In a shallow bowl, stir together the granulated sugar, cinnamon, and nutmeg if using. The nutmeg is subtle but adds bakery depth.

Portion the dough. Scoop 3-tablespoon portions (about 55–60g) for bakery-style size. Roll each portion into a smooth ball, then coat generously in the cinnamon-sugar mix.

Arrange and bake. Space dough balls at least 3 inches apart on the baking sheets. Bake 10–12 minutes, until the edges are set and the centers look slightly underbaked. They’ll continue to set as they cool.

Cool for texture. Let cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool. This step locks in that soft, chewy middle.