1. Preheat oven to 350°F (175°C). Grease and flour a 9-inch round or square cake pan.

2. In a medium bowl, whisk together flour, baking soda, and salt. Set aside.

3. In a large mixing bowl, cream butter and sugars until light and fluffy.

4. Add eggs one at a time, then mix in vanilla, mashed bananas, and sour cream.

5. Gradually add dry ingredients to wet, mixing just until combined.

6. Fold in toasted walnuts, then pour batter into prepared pan.

7. Bake for 35–40 minutes, or until a toothpick comes out clean.

8. Cool cake for 10 minutes in pan, then transfer to a rack to cool completely.

9.

10. For the caramel sauce:

11. In a small saucepan, melt butter and brown sugar over medium heat.

12. Stir in heavy cream and salt, and simmer for 3–4 minutes.

13. Remove from heat and stir in vanilla.

14. Pour warm caramel over the cooled cake before serving.