Preheat oven to 350°F. Grease and flour a 4x8" loaf pan.
In a food processor or bowl, mash the bananas. Add melted butter, baking soda, salt, sugar, egg, vanilla, and flour. Mix until combined and pour into the loaf pan.
Bake for 30 minutes. While baking, prepare the streusel: pulse all topping ingredients until a crumbly texture forms.
After 30 minutes, open the oven and gently spoon the streusel over the top of the bread. Continue baking another 20–30 minutes until a toothpick inserted in the center comes out clean.
Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
Once cool, drizzle with caramel sauce and serve.