01 - Preheat oven to 350°F. Grease a 9×13-inch baking dish or a 9-inch round springform pan with butter or nonstick spray.
02 - In a medium bowl, combine the chopped pecans, packed light brown sugar, ground cinnamon, flour, and melted butter. Stir until the mixture resembles coarse crumbs. Set aside.
03 - In a separate medium bowl, whisk together the 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 on medium speed until pale, light, and fluffy, about 2 to 3 minutes.
05 - Add the eggs one at a time, beating well after each addition until fully incorporated. Mix in the vanilla extract.
06 - Add the dry ingredients and sour cream to the butter mixture in alternating batches, beginning and ending with the flour mixture. Fold gently until just combined — avoid overmixing to keep the cake tender.
07 - Spread half of the batter evenly into the prepared pan. Sprinkle half of the cinnamon pecan crunch mixture over the batter in an even layer. Spread the remaining batter on top and finish with the rest of the pecan crunch mixture.
08 - 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.
09 - Allow the cake to cool in the pan for 20 minutes before slicing. Serve warm or at room temperature.