Preheat oven to 400°F (200°C). Line a 12-cup muffin tin with paper liners or butter the cups. Beat the softened butter and 1 cup sugar with a hand mixer on medium speed until light and fluffy, about 3 minutes.

Add the eggs one at a time, beating well after each, then mix in the vanilla.

Whisk the flour, baking powder, and salt in a separate bowl. Add the dry ingredients to the butter mixture in three additions, alternating with the buttermilk in two additions, starting and ending with the flour. Mix just until combined.

Gently fold in the blueberries with a spatula.

Divide the batter among the muffin cups; they will be nearly full. Sprinkle about 1 teaspoon of sugar over each muffin. Bake until golden and a toothpick comes out clean, 20 to 24 minutes. Cool in the pan 5 minutes, then transfer to a rack. Serve warm.