Step 1: Prepare the Cinnamon Swirl

• In a small bowl, mix brown sugar and ground cinnamon together. Set aside.

Step 2: Make the Batter

• Preheat the oven to 350°F (175°C) and grease a loaf pan.
• In a medium bowl, whisk together flour, baking powder, baking soda, and salt.
• In a separate large bowl, beat the eggs, granulated sugar, and vegetable oil (or melted butter) until smooth.
• Stir in the buttermilk and vanilla extract.
• Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Step 3: Assemble the Bread

• Pour half of the batter into the prepared loaf pan.
• Sprinkle half of the cinnamon sugar mixture over the batter.
• Add the remaining batter on top and sprinkle with the remaining cinnamon sugar mixture.
• Use a knife or skewer to gently swirl the cinnamon sugar into the batter for a marbled effect.

Step 4: Bake

• Bake for 45-50 minutes or until a toothpick inserted into the center comes out clean.
• Allow the bread to cool in the pan for about 10 minutes, then transfer to a wire rack.

Step 5: Add the Glaze

• In a small bowl, whisk together powdered sugar and milk or heavy cream until smooth.
• Drizzle the glaze over the cooled bread before slicing and serving.