Preheat the oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners or lightly grease the cups.
In a large bowl, whisk together the all-purpose flour, granulated sugar, baking powder, baking soda, and salt until well combined.
In a separate medium bowl, whisk the melted butter, buttermilk, eggs, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and gently fold together with a spatula until just combined. Do not overmix; the batter should be slightly lumpy.
Carefully fold in the frozen blueberries, trying not to break them up to avoid coloring the batter.
Divide the batter evenly among the 12 muffin cups, filling each about 3/4 full.
Bake in the preheated oven for 22 to 25 minutes, or until the tops are golden and a toothpick inserted into the center of a muffin comes out clean.
Remove the muffins from the oven and let them cool in the pan for 5 minutes before transferring to a wire rack to cool completely.