Preheat oven to 350°F. Grease a 9x5-inch loaf pan with cooking spray and set aside.

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

In a bowl, beat together the mashed bananas, brown sugar, butter, egg, mayo, rum and vanilla extract with an electric mixer until smooth. Add in the dry ingredients and mix until just combined.

Pour into the prepared pan, smoothing the batter out into an even layer. Top with the sliced banana, cut sides up. Bake for 1 hour and 5 minutes, or until a toothpick, inserted in the middle, comes out clean. Let the bread cool in the pan for 15 minutes before moving to a wire rack to cool completely.

Meanwhile, to make the glaze, cook the butter in a small skillet over medium heat for 2 to 3 minutes, swirling the pan occasionally, until the milk solids begin to brown and smell nutty. Remove the pan from the heat and add in the rum and cook for about 30 seconds to 1 minute, to cook off the alcohol. Transfer the mixture to a bowl and cool. Whisk in the powdered sugar until smooth. Drizzle the sauce over the cooled bread before slicing and serving. Enjoy!