Preheat your oven to 375°F (190°C). This ensures that the muffins bake evenly and rise properly.

Grease a muffin tin with cooking spray or line with muffin liners to prevent sticking.

In a large mixing bowl, whisk together the sifted flour, baking powder, baking soda, salt, and granulated sugar until well combined. This helps to evenly distribute the leavening agents.

In another bowl, whisk together the melted butter, buttermilk, eggs, orange zest, and fresh orange juice until smooth. Mixing wet ingredients separately helps to incorporate them evenly into the dry mixture.

Pour the wet mixture into the dry ingredients. Using a rubber spatula, gently fold the ingredients together until just combined. Be careful not to overmix; a few lumps are okay. Overmixing can lead to dense muffins.

Spoon the batter evenly into the prepared muffin tin, filling each cup about 2/3 full. This allows room for the muffins to rise without overflowing.

Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean. This ensures that the muffins are fully cooked.

Once baked, remove the muffins from the oven and let them cool in the tin for 5 minutes before transferring to a wire rack to cool completely.

Enjoy your fluffy orange muffins warm or at room temperature. They can be stored in an airtight container for up to 3 days.