Preheat oven to 325°F (163°C). Grease and flour a 9×5-inch loaf pan or two smaller loaf pans.
In a large bowl, cream together butter, granulated sugar, and brown sugar until light and fluffy (about 3–4 minutes).
Add eggs one at a time, beating well after each addition. Stir in vanilla extract.
In a separate bowl, whisk together flour, baking powder, salt, and cinnamon.
Gradually add dry ingredients to the wet mixture, alternating with sour cream or buttermilk. Mix just until combined — don’t overmix.
Fold in the chopped pecans.
Pour the batter into the prepared pan(s) and smooth the top.
Optional: Sprinkle the top with cinnamon sugar and chopped pecans for a sweet, crunchy crust.
Bake for 55–65 minutes, or until a toothpick inserted into the center comes out clean.
Cool in the pan for 10–15 minutes before transferring to a wire rack to cool completely.
Serving and Storage Tips:
