For the Streusel
Process the flour, granulated sugar, 1/4 cup of the brown sugar, and the cinnamon in a food processor. Transfer 1 1/4 cups of this mixture to a small bowl and stir in the remaining 1/4 cup brown sugar; set aside.

Add the butter and pecans to the remainig dry ingredients in the food processor bowl. Process the mixture until the nuts and butter have been broken down into small pieces, about ten pulses. Set aside.

For the Cake
Adjust an oven rack to the lowest position and heat the oven to 350 degrees. Grease a tube pan. Combine the eggs, 1 cup of the sour cream, and the vanilla in a medium bowl. In the bowl of a standing mixer, combine the flour, sugar, baking powder, baking soda, and salt at low speed, about 30 seconds. Add the butter and remaining 1/2 cup sour cream and mix at low speed until the dry ingredients are moistened. Increase to medium speed and beat 30 seconds.

Scrape down the sides of the bowl with a rubber spatula. Decrease the mixer speed to medium low and slowly incorporate the egg mixture in 3 additions, beating for 20 seconds after each addition and scraping the sides of the bowl as necessary. Increase the speed to medium-high and beat for 1 minute.

Add 2 cups of the batter to the prepared pan. With an offset spatula or rubber spatula, smooth out the surface of the batter. Sprinkle with 3/4 cup of the streusel filling. Drop 2 cups o the batter over the struesel, spread evenly, and then add the remaining struesel filling. Top with the remaining batter and then the streusel topping (with butter and nuts).

Bake for 50 to 60 minutes. Cool cake for 30 minutes, then invert and remove from tube pan.. Cool or 2 more hours, then serve.