Preheat oven: Preheat oven to 350°F (175°C). Grease or line a 9×5 inch loaf pan.

Combine dry ingredients: Whisk together flour, sugar, baking powder, baking soda, salt, and cinnamon in a large bowl.
Combine wet ingredients: In a separate bowl, whisk together melted butter, eggs, milk, and vanilla extract.
Combine wet and dry ingredients: Gradually add wet ingredients to dry ingredients, stirring until just combined.
Pour into pan: Pour batter into prepared loaf pan.
Bake: Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Add cinnamon sugar topping: While bread is still warm, brush with melted butter and sprinkle with cinnamon sugar mixture.
Cool and serve: Let bread cool in pan for 10-15 minutes before transferring to a wire rack to cool completely. Slice and enjoy!

Enjoy this warm and delicious cinnamon sugar donut sweet bread!