Step 1: Preheat your oven to 350°F (175°C).
Step 2: Line a 12-cup muffin tin with paper liners or grease it lightly.
Step 3: In a large mixing bowl, whisk together the flour, sugar, baking powder, and salt.
Step 4: In a medium bowl, whisk the melted butter, sour cream, egg, orange juice, and zest until smooth.
Step 5: Pour the wet ingredients into the dry ingredients and gently fold together.
Step 6: Scoop the batter into the muffin tin, filling each cup about 2/3 full.
Step 7: Bake for 18-20 minutes, or until a toothpick comes out clean.
Step 8: While baking, whisk together the powdered sugar, orange juice, and zest for the glaze.
Step 9: Cool muffins slightly before glazing with the orange mixture.
