Reduce the apple cider: Pour the apple cider into a small saucepan and simmer over medium heat until it reduces to about 2 tablespoons of thick syrup, 10 to 15 minutes. Set aside to cool completely before using.

Cream butter and sugars: In a large bowl, beat the softened butter with the brown sugar and granulated sugar until light and fluffy, about 2 minutes. The mixture should look pale and smooth.

Add egg and cider syrup: Beat in the egg, vanilla extract, and the cooled apple cider syrup until fully combined and glossy. Scrape down the bowl as needed.

Mix the dry ingredients: In a separate bowl, whisk together the flour, cornstarch, baking soda, cinnamon, nutmeg, and salt until evenly combined.

Combine wet and dry: Add the dry ingredients to the wet mixture and stir just until no dry streaks remain. Avoid overmixing so the cookies stay tender.

Chill if needed: If the dough feels soft or sticky, refrigerate it for 15 to 20 minutes to prevent excess spreading during baking.

Preheat the oven: Preheat your oven to 350°F and line two baking sheets with parchment paper.

Scoop the dough: Scoop the dough into 1.5-tablespoon balls using a cookie scoop or spoon. Roll each ball between your palms until smooth.

Roll in cinnamon sugar: Mix the remaining granulated sugar and cinnamon in a small bowl, then roll each dough ball in the mixture until fully coated.

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

Bake the cookies: Bake for 10 to 12 minutes, until the edges are set and lightly golden but the centers still look slightly underbaked.

Cool and set: Let the cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to finish cooling completely.