• Preheat the oven to 350˚ F.
• Line cupcake pans with paper liners.
• In a medium bowl, combine the flour, baking soda, baking powder, salt and nutmeg; whisk to combine, set side.
• In the bowl of an stand mixer or with a handheld blender, combine the rum, eggnog, vegetable oil, vinegar, and sugar.
• Beat on medium-low speed until well blended, scraping the sides with a spatula as necessary to incorporate all ingredients.
• Add in the dry ingredients, in three additions and mix on low speed just until incorporated.
• With a large ice cream scoop, divide the batter between the prepared cupcake liners, filling the cups 2/3 full.
• Bake 22-24 minutes, or until a toothpick inserted in the center comes out clean.
• Allow to cool in the pan 5 minutes, then transfer to a wire rack to cool completely.

Make the Frosting

• Meanwhile, beat the butter on medium-high speed until smooth, 20-30 seconds.
• Add in the powdered sugar, salt and nutmeg, and mix on medium-high speed until incorporated and smooth, about 1 minute.
• Add in the eggnog and whip on medium-high speed until light and fluffy, 4 minutes.
• With the mixer on medium-low speed, blend in the rum.
• Remove the frosting from the bowl and put into a piping bag. Place if refrigerator for a few minutes if the frosting has become too soft to pipe.
• Frost your eggnog cupcakes as desired.