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 the pecans.
Transfer the batter to the baking dish and, using an offset spatula, spread the batter evenly.
Bake for 30 to 40 minutes, or until a toothpick inserted in the center comes out clean.
For the Cream Cheese Frosting
In your mixer's bowl, combine the 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 the cake from the oven and let it cool completely on a wire rack.
Frost the cooled cake with the Cream Cheese Frosting.
Cut and Serve.
Notes
Room Temperature Ingredients: It's easier to mix the batter when your butter, cream cheese, and eggs are at room temperature. This also helps improve the cake's texture.
Avoid Overmixing the Batter: Combine the ingredients just enough without overdoing it. Overmixing can lead to a dense or tough cake.
Keep an Eye on the Oven: Baking times may vary with different ovens. Start checking your cake around the 32-minute mark. Use a toothpick to test doneness - if it comes out clean, your cake is ready.
Cool Before Frosting: Wait until the cake is completely cool before adding frosting. Frosting it while warm could cause the cake to crumble and become messy.
Adapted from Better Homes and Gardens New Cook Book, Sixteenth Edition