Preheat your oven to 350°F (175°C) and grease a loaf pan.

In a bowl, whisk together the flour, baking powder, and salt.

In another bowl, cream the butter and sugar until light and fluffy. Beat in the egg, milk, vanilla extract, and vegetable oil.

Gradually mix the dry ingredients into the wet ingredients until just combined.

In a small bowl, mix the sugar and cinnamon for the swirl.

Pour half the batter into the loaf pan, sprinkle with half the cinnamon sugar mixture, then add the remaining batter and top with the rest of the cinnamon sugar.

Bake for 45 minutes or until a toothpick inserted into the center comes out clean.

Let cool in the pan for 10 minutes before transferring to a wire rack to cool completely.