Preheat oven to 350°. Line muffin pan with 12 liners & set aside.

In a small bowl, combine the rum, eggnog, vegetable oil, apple cider vinegar, & vanilla extract. Make sure ingredients are well combined. Set aside.

In a large bowl, mix together the nutmeg, sugar, flour, baking soda, baking powder, & salt.

Pour liquid ingredients into dry ingredients & whisk until just combined. Divide evenly into paper liners.

Bake for 18-20 minutes. Cool in pan 5 minutes before transferring to wire rack to cool completely.

For the frosting, cream together the butter, eggnog, rum, nutmeg, & confectioners sugar. Best results if sugar is added in 1/2 cup increments. Add more sugar to stiffen frosting if needed.