Preheat Oven 350 F. Pan Size: 9" Round Or Square Topping: Mix First 3 Ingredients In Med. Bowl. Add Butter And Rub In Until Mixture Resembles Coarse Crumbs. Mix In Nuts. Cake: Cream Sugar And Shortening In Large Bowl. Add Eggs 1 At A Times, Beating Well After Each Addition. Beat In Sour Cream And Vanilla. Sift Flour, Baking Powder, Baking Soda And Salt Together In Bowl. Mix Dry Ingredients Into Shortening Mixture. Spoon Half Of Batter Into Prepared Pan. Sprinkle With Half Of Topping And Swirl Into Batter With Tip Of Knife. Spoon Remaining Batter Over. Sprinkle With Remaining Topping. Bake Until Tester Comes Out Clean, About 40 Minutes. Cool And Serve. *Butter Can Be Substitued For Shortening