Preheat oven to 375°F Generously butter a standard 12-cup muffin pan and dust with flour, tapping out excess; set aside.
In a medium bowl, whisk together flour, baking powder, and salt. Working over the bowl, toss blueberries in a fine sieve with about 1 1/2 teaspoons flour mixture to lightly coat; set aside the flour mixture and the blueberries.
In the bowl of an electric mixer fitted with the paddle attachment, or using a hand held mixer, beat butter and 1 cup sugar on medium-high speed until light and fluffy, about 3 minutes. Add eggs, one at a time, beating until combined. Mix in vanilla.
With the mixer on low speed, add reserved flour mixture, beating until just combined. Add milk, beating until just combined. Do not overmix. Using a rubber spatula, fold in the blueberries. Divide batter evenly among the prepared muffin cups. If desired, in a small bowl, mix together remaining 1/4 cup sugar and nutmeg. Sprinkle sugar mixture on top of muffin batter.
Bake, rotating pan halfway though, until muffins are golden brown and a cake tester inserted in the center of one muffin comes out clean, about 25 minutes. Transfer pan to a wire rack to cool 10 minutes. Turn muffins on their sides in their cups, and let cool. Serve warm or at room temperature.