Preheat oven to 400 degrees.
In a small mixing bowl, whisk together flour, salt, baking powder, and nutmeg.
In a larger mixing bowl, cream butter and sugar together, by hand.
Add in eggs, eggnog, sour cream, and rum extract, whisking together well.
Using a spoon, incorporate the flour mixture into the eggnog mixture, until just combined.
Spray a 12-count muffin tin with cooking spray.
Divide batter evenly between the 12 muffin slots.
Sprinkle 1/4 tsp white sugar on top of each muffin.
Place in oven and bake for 20 minutes.
Remove from oven and allow to cool at least 10 minutes.
Enjoy!