01 - Preheat the oven to 375°F (190°C). Line a standard 12-cup muffin tin with paper liners.
02 - In a large bowl, whisk together all-purpose flour, granulated sugar, baking powder, and salt until well blended.
03 - In a separate medium bowl, whisk the melted unsalted butter, whole milk, eggs, vanilla extract, and lemon zest until smooth.
04 - Pour wet ingredients into the dry mixture. Gently stir until just combined; avoid overmixing.
05 - Fold in the fresh blueberries carefully to prevent crushing them.
06 - Divide batter evenly among the prepared muffin cups, filling each about three-quarters full. Sprinkle with coarse sugar if desired.
07 - Bake in preheated oven for 20 to 25 minutes, or until muffins are golden and a toothpick inserted in the center comes out clean.
08 - Allow muffins to cool in the pan for 5 minutes before transferring to a wire rack to cool completely.