Preheat oven to 350° F. Grease 10-inch angel food tube pan, a bundt pan, or a 9x13 baking dish.
Prepare the filling: In a small bowl, mix together the brown sugar, chopped pecans, and cinnamon. Set aside.
Prepare the streusel topping: In a separate bowl, make the topping by whisking together the sugar, salt, flour, and cinnamon. Add the melted butter, stirring until well combined. The mixture will have large crumbs. Set aside.
Mix the batter: To make the cake, whisk together the flour, baking powder, baking soda, and salt. Set aside. In the bowl of your stand mixer, cream together butter and sugar using the paddle attachment on high speed until light and fluffy. Stir in eggs and vanilla on low speed until combined. Scrape sides down as needed. Beat in the flour mixture alternately with the sour cream. Do not over-mix.
Prepare the cake: Spread 1/3 of the cake batter in the prepared pan. Sprinkle with 1/2 of the filling mixture. Cover with another third of the cake batter, then the remaining filling, and then the remaining cake batter. Sprinkle the topping mixture over the batter in the pan.
Bake: Set the cake in the preheated oven and bake for 55-60 minutes, or until a toothpick inserted into the center of the cake comes out clean. Cool in pan for 10 minutes. If using an angel food tube pan, lift the bottom out of pan (remove sides) to allow the cake to finish cooling. Once completely cool, you can loosen the cake from the center and bottom with a knife and then use a couple spatulas to lift the cake off of the cake pan bottom and transfer to a platter. If using a 9x13" baking dish, the cake can remain in the dish.
Best if served the same or very next day. Store in an airtight container.