In a spacious mixing bowl, cream together softened butter, granulated sugar, and brown sugar until the mixture turns light and fluffy, showcasing a smooth consistency.

Blend in the eggs, eggnog, and either rum or vanilla extract, mixing thoroughly until fully combined.

Gradually incorporate the flour, baking soda, baking powder, cream of tartar, and ground nutmeg. Stir gently until the dough forms and no streaks of flour remain visible. Be careful not to overmix.

Cover the bowl tightly with plastic wrap and refrigerate for at least an hour to allow the dough to firm up.

Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper or a silicone baking mat for even baking and easy cleanup.

In a shallow bowl, mix together the sugar and ground nutmeg for the topping.

Using a tablespoon-sized portion of dough, roll each into a ball. Coat each ball generously in the sugar-nutmeg mixture before placing it on the prepared baking sheet. Space the cookies approximately 2 inches apart to prevent spreading during baking.

Bake for about 10 minutes, or until the edges of the cookies are set and the tops have a slight golden hue.

Remove the cookies from the oven and let them rest on the baking sheet for 3 minutes before transferring them to a wire cooling rack to cool completely.

If desired, sprinkle the cooled cookies with additional freshly ground nutmeg or drizzle with a rich eggnog glaze for an extra touch of festive flavor.