Preheat your oven to 375°F.
Line a 12-cup muffin tin with paper liners or spray with non-stick spray.
In a large bowl, whisk together the flour, baking powder, baking soda, and salt.
In a medium bowl, whisk together the melted butter, sugar, eggs, buttermilk, vanilla extract, lemon zest, and lemon juice.
Pour the wet ingredients into the bowl with the dry ingredients.
Gently stir until just combined. Do not overmix.
In a small bowl, toss the blueberries with 1 tablespoon of flour to coat.
Fold the floured blueberries into the batter gently, using a spatula.
Divide the batter evenly among the 12 muffin cups, filling each about ¾ full.
Bake for 18 to 22 minutes, or until a toothpick inserted into the center comes out clean.
Let the muffins cool in the pan for 5 minutes, then transfer them to a wire rack to cool completely.