Preheat oven to 425°F (220°C). Line a 12-cup muffin tin with paper liners or grease with butter.

In a large bowl, whisk together 2 cups flour, sugar, baking powder, baking soda, and salt until well combined.

In a separate bowl, whisk together melted butter, egg, buttermilk, and vanilla extract until smooth.

In a small bowl, toss blueberries with the remaining 1 tablespoon of flour until evenly coated.

Pour the wet ingredients into the dry ingredients and gently fold together until just barely combined. The batter should still look lumpy - don't overmix.

Gently fold in the flour-coated blueberries until just distributed throughout the batter.

Divide batter evenly among muffin cups, filling each about 3/4 full for bakery-style tops.

Bake for 5 minutes at 425°F, then reduce temperature to 375°F (190°C) and continue baking for 15-18 minutes, until tops are golden brown and a toothpick inserted in center comes out clean or with just a few moist crumbs.

Cool in pan for 5 minutes, then transfer to a wire rack to cool completely before serving.