Preheat the oven to 350°F (175°C) and prepare your cake pans.
In a large bowl, cream the softened butter and sugar together until light and fluffy.
Add the eggs one at a time, mixing well after each addition before incorporating the rest of the ingredients.
Stir in the vanilla extract, and then mix in the buttermilk until just combined.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Gradually fold the dry ingredients into the wet mixture, taking care not to overmix.
Fold in the chopped, toasted pecans gently into the batter.
Divide the batter equally between the prepared cake pans and smooth the tops.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cakes from the oven and let them cool in the pans for about 10 minutes before transferring to a wire rack.
Once completely cool, layer and frost with your favorite buttercream or cream cheese frosting, and top with extra pecans if desired.