Preheat the oven to 350 degrees Fahrenheit and lightly grease a 9x5 inch loaf pan.

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

In a medium bowl, whisk together the eggs, vegetable oil, milk, and vanilla extract until smooth.

Pour the wet ingredients into the dry ingredients and fold gently with a spatula until just combined.

In a small bowl, stir together the brown sugar and cinnamon, then drizzle in the melted butter and mix until damp and sandy.

Spread half of the batter into the prepared pan, sprinkle half of the cinnamon mixture over it, pour the remaining batter, then sprinkle the rest of the cinnamon mixture and swirl with a knife.

Bake for 45 to 50 minutes until the top is golden and a toothpick inserted into the center comes out with a few moist crumbs; tent with foil if browning too quickly.

Let the bread rest in the pan for 10 minutes, then transfer to a cooling rack and cool completely, about 30 minutes.

Whisk together the powdered sugar, milk, and vanilla extract until you reach a pourable but not runny consistency.

Drizzle the glaze over the cooled loaf and let it set before slicing.