Preheat the oven to 350°F (175°C) and grease two 8-inch round cake pans.
In a bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, and nutmeg.
In another bowl, beat butter and brown sugar until fluffy. Add eggs, maple syrup, and vanilla, mixing until smooth.
Gradually add dry ingredients, alternating with buttermilk, and beat until combined.
Fold in the chopped pecans.
Pour the batter evenly into the prepared pans and bake for 35-40 minutes, or until a toothpick comes out clean.
Let the cakes cool in the pans for 10 minutes, then transfer to a cooling rack to cool completely.
For the frosting, beat butter, powdered sugar, maple syrup, and vanilla until smooth.
Frost the cooled cakes, topping with the remaining chopped pecans.