Preheat the oven to 350F degrees. Grease a 9x5 loaf pan with nonstick cooking spray. Set aside.
In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
With a mixer, cream together the butter and brown sugar on medium speed, about 3 minutes. Add the eggs one at a time, beating well after each addition. Beat in the vanilla extract and mashed bananas. With the mixer on low, mix in half of the dry ingredients. Add the milk, once milk is combined mix in the rest of the dry ingredients. Mix until just combined. Don't overmix.
Spoon the batter into the prepared baking pan and drizzle salted caramel sauce over the batter. Use a knife to swirl in the salted caramel sauce.
In a small bowl, combine flour, brown sugar, and cold butter pieces. Rub the mixture together with your fingers until combined and crumbly. Stir in the cashew pieces. Sprinkle streusel topping over the batter in the pan.
Bake for 60-65 minutes, loosely covering the bread with aluminum foil during the last 15 minutes if the top of the bread is getting to dark. A toothpick inserted in the center of the loaf will come out clean when the bread is done. Remove from the oven and allow the bread to cool for 15 minutes on a wire cooling rack. Use a knife to loosen the bread around the edges in the pan. Carefully remove the bread from the pan and cool completely.
Note-the bread will keep covered on the counter for up to 4 days. Can freeze the loaf for up to 2 months.