Preheat oven to 350°F. Coat a 9×9 baking dish with nonstick spray. Set aside.
Streusel: Combine melted butter, brown sugar, cinnamon, salt, flour, and pecans in a medium bowl. Stir until evenly combined. Set aside.
Cake: In the bowl of your stand mixer fitted with thepaddle attachment mix the butter and the sugar together on medium speed for 2 minutes. Add in the eggs and continue mixing on medium for 2 more minutes, scraping the sides of the bowl as necessary.
Add in the vanilla, sour cream, salt, baking powder, and baking soda. Mix for 1 minute until combined.