In a small bowl, stir together the brown sugar, pecans, and cinnamon.
For the cake:
Preheat oven to 350°F. Grease an angel food cake pan with nonstick cooking spray.
In a large bowl, cream together the butter and sugar using a handheld mixer. Beat until the mixture is light and fluffy, about 2 minutes.
Crack eggs into the mixture and beat well.
Add the sour cream and mix until combined. Stir in the flour, baking powder, baking soda, and salt. You can either do this by hand or with the mixer, but if you use the mixer, be careful not to overbeat it—mix it just until combined.
Pour half of the batter into the greased angel food cake pan and spread evenly across the bottom.
Sprinkle half of the pecan topping on top. Spread the remaining batter on top of the pecan topping, and then top with the remaining pecan topping.
Bake for 38–42 minutes in the preheated oven, or until golden brown.