Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a large mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy (about 3-4 minutes).
Add the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the butter mixture, alternating with the buttermilk, beginning and ending with the flour mixture. Mix until just combined.
Fold in the toasted pecans gently.
Divide the batter evenly between the prepared cake pans.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cakes to cool in the pans for 10 minutes before transferring them to a wire rack to cool completely.
Serve the cake plain or with a dusting of powdered sugar.