Preheat oven to 350 and grease a 9x9 baking pan with nonstick cooking spray. Set aside.Beat together butter and sugar until fluffy, about 3 minutes. Add eggs and beat well.
Add half of the dry ingredients with half of the buttermilk and beat just until combined. Repeat a second time until the ingredients are all incorporated into the batter.
Spoon mixture into prepared pan and spread evenly. Bake for 36-40 minutes or until edges are brown and a toothpick inserted in the center comes out clean.