Preheat your oven to 350°F (175°C) and grease a 9x5-inch loaf pan.

Whisk together the flour, baking powder, salt, and cinnamon.

Cream together the unsalted butter and granulated sugar until light and fluffy.

Add eggs one at a time, mixing well after each addition. Then add milk and vanilla.

Gradually add the dry mixture to the wet mixture until just combined.

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

Gently swirl a knife through the batter and bake for 50-60 minutes until a toothpick comes out clean.

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