Preheat your oven to 400°F (200°C). Line a 12-cup muffin pan with paper liners.

In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until well combined.

In a separate medium mixing bowl, whisk together the egg, whole milk, melted and cooled unsalted butter, and lemon zest until just combined.

Pour the wet ingredients into the dry ingredients. Mix with a rubber spatula just until the ingredients are barely combined. Be careful not to overmix; a few lumps are perfectly fine and will result in tender muffins.

Gently fold in the flour-tossed fresh blueberries. Tossing them in a little flour beforehand helps prevent them from sinking to the bottom of the muffins during baking.

Divide the muffin batter evenly among the 12 prepared muffin cups, filling each approximately two-thirds full.

Bake for 5 minutes at 400°F (200°C), then reduce the oven temperature to 375°F (190°C) and continue to bake for another 17-20 minutes, or until the tops are golden brown and a toothpick inserted into the center of a muffin comes out clean.

Let the muffins cool in the muffin pan for 5 minutes before carefully transferring them to a wire rack to cool completely.

While the muffins cool, prepare the lemon glaze. In a small bowl, whisk together the powdered sugar and 2 tablespoons of fresh lemon juice until smooth. Add more lemon juice, a teaspoon at a time, if a thinner consistency is desired.

Once the muffins are mostly cooled, drizzle the lemon glaze generously over the tops. Allow the glaze to set slightly before serving.