Cream butter and sugar until light and fluffy.

Beat in eggs one at a time, mixing well after each addition.

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

Gradually add the dry ingredients to the wet ingredients, alternating with milk, until just combined.

Stir in vanilla extract.

Grease a tube or bundt pan.

Pour batter into the prepared pan.

In a small bowl, combine cinnamon and sugar.

Sprinkle cinnamon sugar mixture evenly over the batter.

Use a fork to swirl the cinnamon sugar into the batter in an up and down motion.

Bake in a preheated oven at 350 degrees F (175 degrees C) for 50 minutes, or until a wooden skewer inserted into the center comes out clean.

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