Preheat your oven to 350℉ (175℃). Lightly grease 15 muffin cups or line them with paper liners.

In a small bowl, whisk together the gluten-free flour blend, baking powder, and salt. Set aside.

In a large mixing bowl, combine softened butter and granulated sugar. Beat on medium-low speed until thick and creamy.

Add eggs one at a time while mixing until fully combined.

Gradually add the dry ingredients to the butter-sugar mixture and mix until a thick batter forms.

Stop the mixer and stir in the milk and vanilla extract until everything is combined and creamy.

Carefully fold in the blueberries using a rubber spatula.

Spoon the batter into the prepared muffin pans, filling each cavity about two-thirds full. If desired, sprinkle about 1 teaspoon of granulated sugar on top of each muffin.

Bake for about 25 minutes or until a cake tester inserted in the center comes out clean.

Let the muffins cool in the pan for about five minutes before transferring them to a wire rack.