Preheat your oven to 350°F (175°C) and grease an 8.5-by-4.5-inch loaf pan with nonstick cooking spray.

Melt the stick of unsalted butter in a light-colored sauté pan over medium heat for about 4-5 minutes, stirring frequently until golden brown.

In a large mixing bowl, mash the 3 ripe bananas until smooth, then whisk in the 3 large eggs.

In another bowl, whisk together the flour, dark brown sugar, baking powder, cinnamon, nutmeg, and salt.

Gently combine the banana-egg mixture with the dry ingredients and stir until just mixed; drizzle in the cooled brown butter.

Pour the batter into the prepared loaf pan, placing the halved banana on top and sprinkling with brown sugar.

Bake in the preheated oven for 70 to 80 minutes, checking for doneness with a toothpick.

Cool in the pan for 10-15 minutes before transferring to a wire rack to cool completely.