1. Preheat your oven to 350°F (175°C). Grease a 9×5-inch loaf pan or line it with parchment paper.

2. In a small bowl, mix together the brown sugar and ground cinnamon for the swirl. Set aside.

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

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

5. Combine the wet and dry ingredients, mixing just until blended. Do not overmix.

6. Pour half the batter into the prepared pan. Sprinkle half of the cinnamon-sugar mix over it.

7. Add the remaining batter, followed by the rest of the cinnamon mixture. Swirl gently with a butter knife.

8. Bake for 45 to 55 minutes or until a toothpick inserted in the center comes out clean.

9. Let the cake cool in the pan for 10 minutes, then remove and cool completely on a wire rack.

10. (Optional) Whisk together powdered sugar and milk to make a glaze and drizzle over the cooled cake.