Preheat your oven to 350°F and grease a loaf pan.
In a small bowl, mix together ⅓ cup of the sugar and the cinnamon.
In a larger bowl, combine the flour, baking powder, salt, and the remaining 1 cup sugar.
Add the egg, milk, and vegetable oil, then stir until the batter comes together.
Pour half of the batter into the loaf pan and sprinkle in half of the cinnamon sugar mixture.
Add the remaining batter on top, then finish with the rest of the cinnamon sugar.
Use a toothpick or knife to create swirls on top.
Bake until golden and a toothpick comes out clean, about 50 to 60 minutes.
Let cool slightly, then slice and enjoy.
