Preheat oven to 350°F. Spray an 8 ½ x 4 ½-inch loaf pan with nonstick cooking spray.
In a large mixing bowl, combine the flour, granulated sugar, baking powder, salt, and ground nutmeg.
In a separate bowl, whisk together the milk, egg, melted butter, and vanilla until well combined.
Pour the milk mixture into the flour mixture and stir gently until just combined. Be careful not to overmix; the batter should be a bit runny.
Pour the batter into the prepared loaf pan, spreading it evenly.
Bake for 60 to 70 minutes, or until a toothpick inserted into the center comes out with a few crumbs and the top is golden brown.
Once baked, remove the bread from the oven and let it cool in the pan for about 10 minutes. Then, carefully remove the bread from the pan and place it on a wire rack set over parchment paper (to catch drips).
In a medium bowl, whisk together confectioners' sugar, 4 tablespoons milk, vanilla extract, and a pinch of salt until smooth. If too thick, add milk ½ tablespoon at a time until pourable. (It should be thick but drizzle easily.)
While the bread is still slightly warm, pour or spoon the glaze generously over the top, letting it drip down the sides. For full donut-style coverage, you can dip the top directly into the glaze or brush on extra layers.
Let the glaze set for 20 to 30 minutes before slicing and serving.
