Preheat oven to 325°F. In medium bowl, combine flour, baking soda and salt. In separate bowl, whisk together oil, buttermilk, eggs and vanilla. Stir in sugar, pineapple and, if desired, nuts. Add flour mixture; mix well. Pour into prepared pan.
Bake 20-25 minutes or until toothpick inserted comes out clean. Cool 10 minutes in pan on rack; remove and cool completely before decorating.