Preheat the oven to 375°F (190°C). Line a muffin tin with paper liners or grease with non-stick spray.
Mix the dry ingredients – In a large bowl, whisk together the flour, sugars, baking powder, baking soda, and salt.
Prepare the wet ingredients – In a separate bowl, whisk the melted butter, eggs, vanilla extract, and buttermilk until smooth.
Combine the mixtures – Pour the wet ingredients into the dry ingredients. Use a spatula to gently mix until just combined. Don’t overmix, or the muffins may become dense.
Prepare the blueberries – Toss the blueberries with 1 tablespoon of flour (this helps prevent them from sinking to the bottom). Fold them gently into the batter.
Fill the muffin cups – Divide the batter evenly among the 12 muffin cups, filling each about ¾ full.
Bake for 18-22 minutes, or until a toothpick inserted in the center comes out clean.
Cool and enjoy – Let the muffins cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely. Enjoy warm or at room temperature!