Preheat your oven to 350°F (175°C) and grease a 9×5-inch loaf pan.
In a medium bowl, mash the ripe bananas until smooth. In a large bowl, whisk together melted butter, white sugar, brown sugar, beaten eggs, vanilla extract, buttermilk, and mashed bananas until combined.
In another bowl, whisk together flour, baking soda, baking powder, salt, cinnamon, and nutmeg.
Gently fold dry ingredients into the wet mixture until just combined; avoid overmixing. Fold in one tablespoon of caramel syrup for swirls.
Pour the batter into the prepared loaf pan and bake for 55-65 minutes or until a skewer comes out clean.
Let cool in the pan for about 10 minutes before transferring to a wire rack. Drizzle remaining caramel syrup and sprinkle with sea salt before slicing.