Preheat the oven to 350 degrees, grease and flour three 8x2 inch round cake pans.
In a medium size bowl, add the flour, baking powder, baking soda and salt. Use a whisk to blend, set aside.
In another bowl or 4 cup measuring cup add the buttermilk, oil and vanilla, set aside.
In the bowl for you mixer, mix the butter until til smooth. Gradually add the sugar and mix at medium speed for 3 to 5 minutes (a bit longer if using a hand mixer) until it is lightened in color and fluffy.
Add the room temperature eggs one at a time, mixing after each until the yellow of the yolk has blended.
With the mixer on low speed, add the flour mixture and the buttermilk mixture alternately, beginning and ending with flour mixture ( Three additions of dry, two additions of wet.) Mix just until combined.
Fold in the chopped pecans
Bake at 350 degrees for 22 to 25 minutes or until a toothpick inserted into the center comes out clean or with just a few crumbs attached. Let cakes cool 5 to 10 minutes then turn out.