Preheat the oven to 375°F (190°C) and grease or line a muffin tin with paper liners.

In a large bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.

In another bowl, combine the melted butter, buttermilk, eggs, and vanilla extract.

Pour the wet ingredients into the dry ingredients and mix until just combined.

Gently fold in the blueberries.

Divide the batter evenly among the muffin cups.

Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.

Remove from the oven and let cool in the pan for 5 minutes before transferring to a cooling rack.