01 - Preheat the oven to 350°F. Grease a 9x13-inch baking dish or a 9-inch round springform pan with butter or non-stick spray.
02 - In a medium bowl, combine the chopped pecans, packed light brown sugar, ground cinnamon, all-purpose flour, and melted butter. Mix until the mixture resembles coarse crumbs and set aside.
03 - In a separate medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until evenly distributed.
04 - In a large mixing bowl, beat the softened butter and granulated sugar using an electric mixer until pale, light, and fluffy, approximately 3 minutes.
05 - Add the eggs one at a time, beating well after each addition until fully incorporated. Stir in the vanilla extract.
06 - Alternately add the dry flour mixture and the sour cream to the butter mixture, beginning and ending with the flour mixture. Fold gently until just combined, being careful not to overmix.
07 - Spread half of the cake batter evenly into the prepared pan. Sprinkle half of the cinnamon pecan crunch mixture uniformly over the batter.
08 - Carefully spread the remaining batter over the pecan layer, then top with the remaining crunch mixture, pressing gently to adhere.
09 - Bake for 40 to 45 minutes, or until a toothpick inserted into the center of the cake comes out clean and the top is golden brown.
10 - Allow the cake to cool in the pan for 20 minutes before slicing into portions and serving warm.