Step 1: Preheat Your Oven - Preheat your oven to 375°F (190°C) and line a muffin tin with paper liners or grease it lightly with cooking spray.
Step 2: Prepare the Wet Ingredients - In a large mixing bowl, whisk together the melted unsalted butter, milk, grated orange zest, vanilla extract, and eggs until well combined.
Step 3: Mix the Dry Ingredients - In another bowl, combine the all-purpose flour, granulated sugar, baking powder, and salt. Stir these dry ingredients until they are evenly mixed.
Step 4: Combine Wet and Dry Ingredients - Gently fold the dry ingredients into the wet ingredients using a rubber spatula. Be careful not to overmix; it’s okay if there are a few lumps.
Step 5: Add Blueberries - Fold in ¾ cup of the fresh blueberries, being gentle to avoid breaking them. Set aside the remaining blueberries for topping.
Step 6: Fill Muffin Tin - Spoon the muffin batter evenly into the prepared muffin tin, filling each cup about ¾ full. Top each muffin with a few of the reserved blueberries for a pretty presentation.
Step 7: Bake - Place the muffin tin in the preheated oven and bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean.
Step 8: Cool and Enjoy - Once baked, remove the muffins from the oven and allow them to cool in the pan for 5 minutes. Then, transfer them to a wire rack to cool completely. Enjoy warm or at room temperature!