Preheat oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.
In a large bowl, cream together the butter and brown sugar until light and fluffy.
Beat in the maple syrup, then add the eggs one at a time, beating well after each addition.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet mixture, alternating with the buttermilk, beginning and ending with the dry ingredients.
Fold in the chopped pecans.
Pour the batter into the prepared pan and smooth the top.
Bake for 35 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool in the pan for 10 minutes, then turn out onto a wire rack to cool completely.