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

In a mixing 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.

Scoop the batter into the prepared muffin tin, filling each cup about 2/3 full.

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

Allow the muffins to cool in the tin for 5 minutes before transferring to a wire rack.