Preheat oven to 350˚F.
Lightly grease a 9x13 glass baking dish with cooking spray; set aside.
In a large mixing bowl beat butter on high until creamy; about 30 seconds.
Add sugar, baking powder, baking soda, and salt; beat until combined.
Add egg, mashed bananas, sour cream and vanilla; beat until incorporated.
Mix in the flour; continue to mix until combined.
Stir in pecans.
Transfer batter to previously prepared baking dish and, using an offset spatula, spread batter evenly.
Bake for 30 to 40 minutes, or until a toothpick inserted in the center comes out clean.
In the meantime, prepare the Cream Cheese Frosting.
In your mixer's bowl, combine cream cheese, butter and vanilla; mix until fluffy and completely combined.
Slowly add powdered sugar, about 1/3-cup at a time; continue to mix until smooth and thoroughly incorporated.
Remove cake from oven and let cool on a wire rack.
Frost cooled cake with previously prepared Cream Cheese Frosting.
Cut and Serve.