Preheat oven to 350F
In a large bowl mix melted butter and sugar until combined
Add egg and vanilla and mix well
Add greek yogurt and mix well
Add dry ingredients (flour, baking powder, salt) and fold to combine
Add milk and mix until smooth
Add ½ of batter to a lined loaf tin
Sprinkle ¾ of the cinnamon sugar mixture over the batter
Add remaining batter to the loaf tin
Top with remaining ¼ cinnamon sugar mixture
Bake at 350F for 55 minutes or until a toothpick comes out clean
Top with optional icing made from powdered sugar and milk
