Preheat oven to 350°F (175°C). Grease a 9×5-inch loaf pan or line it with parchment paper.

In a medium bowl, whisk together flour, baking powder, nutmeg, and salt.

In a large bowl, beat butter and sugar until light and fluffy.

Add eggs one at a time, mixing well after each, then stir in vanilla extract.

Alternately add the dry mixture and eggnog to the wet ingredients, mixing until just combined.

Pour batter into the prepared pan and smooth the top.

Bake for 50–60 minutes, or until a toothpick inserted in the center comes out clean.

Let the loaf cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.

Whisk powdered sugar and eggnog until smooth, then drizzle over cooled bread. Let set before slicing.