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

Whisk together the dry ingredients in a bowl: flour, baking powder, cinnamon, and salt.

Cream the softened butter and granulated sugar until fluffy and light. Add eggs one at a time, mixing well, then blend in the sour cream.

Combine the dry ingredients with the wet ingredients gradually. Stir until just mixed.

Layer the batter, pour half into the prepared pan, sprinkle with half the cinnamon-sugar mixture, then add remaining batter. Top with leftover cinnamon-sugar.

Bake for 50-60 minutes until golden brown and a toothpick comes out clean. Cool for 10 minutes before transferring to a wire rack.