Preheat the oven to 350°F. Grease and flour an 8x4-inch loaf pan.
In a small bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a medium bowl, using an electric mixer, beat the butter until smooth, then slowly add the maple syrup, mixing constantly. By hand, whisk in the sour cream and egg. Stir in the pecans (if using). Add the flour mixture and stir just until blended (do not over-mix).
Spoon the batter into the prepared loaf pan and bake in the preheated oven until a toothpick inserted into the center of the loaf comes out clean, 50 to 60 minutes. Transfer the pan to a wire rack and cool for 15 minutes, then turn the loaf out onto the rack to cool completely.
Notes
Nutritional information does not include the optional pecans.