Preheat oven to 200 degrees Celsius.

In a large bowl, mix together flour, baking powder, and baking soda.

In another bowl, add the melted butter, sugar, mashed banana, vanilla, eggs, milk, orange juice, and orange rind.

Mix the wet ingredients with a fork until combined.

Pour the wet ingredients into the dry ingredients and fold together until just barely damp, being careful not to overmix.

Gently stir in the blueberries, avoiding overmixing.

Spoon the mixture into deep, buttered or sprayed muffin pans.

Sprinkle each muffin with 1/4 teaspoon of cinnamon sugar.

Bake for 10-12 minutes, or until muffins spring back when pressed in the center.