Preheat oven to 350. Grease and flour a 10-inch tube pan; set aside.
All ingredients should be at room temperature.
For topping, mix together flour, sugar, salt and nuts. Add butter. Rub in by hand until mixture is crumbly. Be careful not to over mix.
For cake, in bowl mix together cake flour, flour, soda and baking powder.
In another bowl cream together butter with sugar until fluffy and light.
Add egg and vanilla and mix well.
Add half of dry ingredients, mixing just until flour is blended.
Blend in sour cream, then remaining dry ingredients.
Spread half of batter lightly into prepared baking pan. Sprinkle with half of topping and spread with remaining batter. Sprinkle with remaining Topping.
Bake for 40-45 minutes or until tested done when wooden pick inserted in center comes out clean.