Preheat oven to 180 degrees Celsius and grease a 12-cup muffin tin.

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

In a medium bowl, whisk together the melted butter and sugar until combined. Add in the eggs and vanilla extract, mixing to combine.

Slowly add in the buttermilk and stir until combined. Gently fold in the dry ingredients until just combined. Finally, fold in the frozen blueberries.

Divide the muffin batter among the prepared muffin cups. Bake in preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Let cool before serving. Enjoy!