1. Prepare the Crust:

1. Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans.
2. In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
3. In a large bowl, cream the butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract and mashed bananas.
4. Gradually add the dry ingredients to the wet ingredients, alternating with the sour cream, beginning and ending with the dry ingredients. Fold in the chopped pecans.
5. Divide the batter evenly between the prepared cake pans and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes, then turn out onto wire racks to cool completely.
6. To assemble the cake, place one layer on a serving plate and spread half of the caramel sauce over it. Place the second layer on top and spread the remaining caramel sauce over the top. Garnish with additional chopped pecans if desired.