Preheat the oven to 350°F (175°C). Grease and flour the loaf pan, or line it with parchment paper for easy removal.
In a large mixing bowl, combine the flour, sugar, baking powder, baking soda, salt, and ground cinnamon. Whisk together until well combined.
In another bowl, cream together the softened butter, eggs, and vanilla extract until smooth and fluffy.
Gradually add the dry ingredients to the wet mixture, alternating with the buttermilk. Begin and end with the dry ingredients. Mix until just combined; do not overmix.
Gently fold in the chopped pecans until evenly distributed in the batter.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake in the preheated oven for 55-60 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the bread from the oven and allow it to cool in the pan for 10 minutes. Then turn it out onto a cooling rack to cool completely.