1. Preheat oven to 350ºF.
2. Sift flour, baking powder, baking soda, cinnamon and salt together, set aside.
3. Cream margarine & sugars, add eggs and beat well.
4. Add flour mixture alternately with buttermilk.
5. Spread in well-greased 9" x 13" pan.
6. Combine topping ingredients and spread over batter.
7.
Cover pan with foil and refrigerate for 8 hours.
8. Bake for about 45 minutes.