Step 1: Preheat & Prep

1. Preheat oven to 350°F (175°C).
2. Grease and flour a 9×5-inch loaf pan or use parchment paper.

Step 2: Make the Batter

1. In a large mixing bowl, whisk together flour, sugar, baking powder, baking soda, and salt.
2. In another bowl, whisk eggs, buttermilk, melted butter, and vanilla extract.
3. Slowly mix wet ingredients into the dry ingredients until smooth (don’t overmix!).

Step 3: Add the Cinnamon Swirl

1. In a small bowl, mix brown sugar and cinnamon together.
2. Pour half the batter into the loaf pan.
3. Sprinkle half the cinnamon sugar mixture over the batter.
4. Add the rest of the batter on top, then sprinkle the remaining cinnamon sugar.
5. Use a knife or skewer to swirl the cinnamon sugar into the batter for that beautiful marbled effect.

Step 4: Bake the Bread

1. Place in the oven and bake for 45-50 minutes, or until a toothpick inserted in the center comes out clean.
2. Let it cool in the pan for 10 minutes, then transfer to a wire rack.

Step 5: Coat with Cinnamon Sugar

1. Brush the top with melted butter.
2. In a small bowl, mix granulated sugar and cinnamon.
3. Sprinkle the cinnamon sugar mixture over the top, or roll the entire loaf in the sugar mixture for a full donut-like effect.