Preheat oven to 375°.
Combine flour, sugar, baking powder, and baking soda in a mixing bowl.
Add buttermilk, butter, orange rind, vanilla, egg, and sour cream, stirring just until moistened.
Spoon batter into lightly greased muffin pans.
Stir together all the topping ingredients.
Sprinkle topping over batter.
Bake at 375° for 15-20 minutes or until lightly browned.Remove muffins from pans and cool on wire rack.