Preheat your oven to 375°F.
Grease a 12-cup muffin tin or line it with cupcake papers.
In a mixing bowl, combine melted butter and sugar until well incorporated.
Add the beaten eggs, baking powder, and salt, and mix thoroughly.
Place 1 tablespoon of flour in a plastic bag with the blueberries.
Gently shake to coat them, which helps prevent sinking during baking.
Set aside after coating.
Fold the prepared flour into the wet mixture.
Once combined, carefully fold in the coated blueberries.
Divide the batter evenly among the muffin cups.
Bake until a toothpick inserted into the center of a muffin comes out clean, about 20-25 minutes.