Pre-heat oven to 350.
Grease and flour a large rectangular cake pan or 2 round baking pans.
Stir together dry ingredients.
Combine sugar, butter, eggs, applesauce and buttermilk.
Stir in dry ingredients and mix thoroughly.
Cut butter into topping ingredients.
Add walnut pieces to topping ingredients.
Sprinkle over batter.
Bake until a tester placed in the center comes out clean.