Preheat the oven to 180°C and grease a 12-cup muffin tray. Mix flour, baking powder, baking soda, and salt in a large bowl and set aside.
Mix melted butter, sugar, eggs, buttermilk, and vanilla extract in a medium bowl until smooth.
Add the mixture to the flour mixture and fold in carefully, not mixing the mixture too much so that the muffins are nice and fluffy and rise well. Finally, add the blueberries and fold them in just briefly and carefully.
Using a large spoon or ice cream scoop, spread the dough over the 12 muffin tins and fill to the brim. The dough should be thick and form a small hill, the muffins will then be slightly larger.
Bake the muffins at 180°C for approx. 20 minutes or until no more dough remains stuck during the stick test. Remove the muffins from the oven and sprinkle them with sugar while they are still warm, let them cool and enjoy!