1. Preheat the oven to 350°F and grease a 9×5-inch loaf pan.

2. In a small bowl, mix the brown sugar and cinnamon to make the swirl filling.

3. In a large bowl, whisk together the flour, granulated sugar, baking powder, and salt.

4. In another bowl, whisk the eggs, milk, melted butter, and vanilla extract until smooth.

5. Pour the wet ingredients into the dry ingredients and stir just until combined.

6. Spread one-third of the batter into the prepared loaf pan and sprinkle with one-third of the cinnamon sugar mixture.

7. Repeat the layers two more times, ending with the cinnamon sugar on top.

8. Use a butter knife to gently swirl through the batter a few times to create a marbled effect.

9. Bake for 50 to 60 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs.

10. Cool the bread in the pan for 15 minutes, then transfer it to a wire rack.

11. Whisk the powdered sugar, milk, and vanilla extract until smooth.

12. Drizzle the glaze over the cooled bread, then slice and serve.