Preheat your oven to 350°F (175°C) and grease your loaf pan or line it with parchment paper for easy removal.
In a large mixing bowl, combine the light brown sugar, canola oil, and granulated sugar. Whisk this mixture until well combined. Then, add the egg, sour cream, instant espresso granules, and vanilla extract, mixing until smooth.
Fold in the mashed ripe bananas into the wet mixture, ensuring they’re evenly distributed throughout.
In a separate bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Gradually add the dry ingredients to the wet mixture, stirring gently until just combined to avoid overmixing.
Drizzle in the caramel sauce and gently swirl it through the batter. Be careful not to fully mix it in; you want to see ribbons of caramel throughout the bread.
Pour the batter into your prepared loaf pan, smoothing the top with a spatula.
In a small saucepan over low heat, melt the unsalted butter and mix in the light brown sugar, vanilla extract, and a pinch of salt (if desired). Stir until combined, then drizzle this mixture over the top of the batter in the loaf pan.
Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean. If the top is browning too quickly, you can cover it loosely with foil for the last 15 minutes of baking.
Once baked, allow the bread to cool in the pan for about 10 minutes before transferring it to a wire rack. Let it cool completely before slicing.