Apple Walnut Coffee Cake
* 1 cup walnuts, finely chopped
* ½ cup light packed brown sugar
* 1 ¼ tsp cinnamon
* 1 tbsp all purpose flour
* 2 tbsp butter, slightly softened
* 2 cups all purpose flour
* 1 tsp baking soda
* 1 tsp baking powder
* ½ tsp salt
* ½ cup butter, softened
* 1 cup sugar
* 2 egg
* 1 tsp vanilla extract
* ½ tsp lemon zest
* 1 cup sour cream
* 2 to 2 ½ cups granny smith apple, diced
1) Make the walnut topping: In a bowl, combine walnuts, brown sugar, cinnamon and flour. Add the butter and crumble between your fingertips until the mixture forms coarse crumbs. Refrigerate mixture while preparing cake batter.
2) Make the apple cake: Pre-heat oven to 350◦F. Grease and flour the bottom and sides of a 9×13-inch rectangular cake pan or a 10-inch springform pan.
3) Sift together the flour, baking soda, baking powder and salt.
4) In the bowl of an electric mixer, cream together butter and sugar until the mixture becomes light. Beat the eggs one at a time, beating well after each addition. Add the vanilla and lemon zest.
5) At lowest speed of the mixer, beat in flour mixture alternately with the sour cream.
6) Fold in apples by hand just until evenly distributed in the batter.
7) Pour into prepared baking pan. Sprinkle the top evenly with the prepared walnut mixture.
8) Bake for approximately 40 to 50 minutes for a rectangular pan and 45 to 55 minutes for a 10-inch spring form pan or until a toothpick inserted into the center of the cake comes out clean.