Step 1: Preheat your oven to 350°F (175°C) and grease your loaf pan with butter or line it with parchment paper for easy removal.
Step 2: In a small bowl, combine the brown sugar and cinnamon. This will be used to create a delightful swirl in your loaf.
Step 3: In a large mixing bowl, whisk together the flour, baking powder, baking soda, and salt until well combined. Set aside.
Step 4: In another large bowl, beat the softened butter, granulated sugar, and brown sugar mixture until light and fluffy, about 3-4 minutes.
Step 5: Add the eggs one at a time, mixing well after each addition. Then, stir in the vanilla extract.
Step 6: Mix in the buttermilk until thoroughly combined.
Step 7: Gradually add the dry flour mixture to the wet ingredients, stirring gently until just combined. Be careful not to overmix; some lumps are okay!
Step 8: Pour half of the batter into the prepared loaf pan. Sprinkle half of the cinnamon-sugar mixture on top. Pour the remaining batter over the cinnamon layer and finish with the rest of the cinnamon-sugar mixture on top.
Step 9: Place the loaf in the preheated oven and bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean.
Step 10: Once baked, remove the loaf from the oven and let it cool in the pan for 10 minutes. Then, transfer it to a wire rack to cool completely before slicing.
