Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan or line it with parchment paper for easy cleanup.
In a medium bowl, whisk together the flour, sugar, baking powder, baking soda, salt, and cinnamon. Set aside.
In a separate bowl, whisk together the buttermilk, melted butter, eggs, and vanilla extract until smooth.
Gradually add the dry ingredients to the wet ingredients, mixing gently until just combined. Do not overmix—the batter should be slightly lumpy.
Pour the batter into the prepared loaf pan, smoothing the top with a spatula. Bake in the preheated oven for 45–50 minutes, or until a toothpick inserted into the center comes out clean. Let the bread cool in the pan for 10 minutes before transferring it to a wire rack.
While the bread is still warm, brush the entire surface with melted butter using a pastry brush. In a small bowl, mix together the granulated sugar and cinnamon. Sprinkle the mixture generously over the buttered bread, patting gently to help it adhere.
In a small bowl, whisk together the powdered sugar, milk, and vanilla extract until smooth. Adjust the milk to achieve your desired consistency. Drizzle the glaze over the cooled bread for an extra touch of sweetness.
Slice the bread and serve it warm or at room temperature. Enjoy the donut-like flavors in every bite!
