Spray a 9x5-inch loaf pan with nonstick spray.
Set the oven rack to middle position and heat oven to 350°F.
Heat a heavy saucepan over medium heat.
Add the butter and whisk until melted, stirring often.
6 tablespoons Danish Creamery European Style Unsalted Butter
Allow to continue to cook while whisking often until the butter starts to froth and bubble.
You'll see specks of darker color forming at the bottom.
Once the butter is a golden brown color and you smell a nutty aroma, immediately remove from the heat and set aside.
In a large bowl, whisk the flour, sugar, baking soda, and salt together; set aside.
2 cups all-purpose flour, ¾ cup brown sugar, ¾ teaspoon baking soda, 1 teaspoon kosher salt
In a separate medium mixing bowl, mash the very ripe bananas, sour cream, browned butter, and vanilla together.
3 very ripe bananas, ¼ cup sour cream, 1 teaspoon pure vanilla extract
Lightly fold the mashed banana mixture into the flour mixture with a rubber spatula. Mix the batter just until combined – it should be lumpy and thick.
Transfer the batter to the prepared pan, smooth out the top and, if desired, arrange ripe banana slices on top.
1 ripe banana
Bake 60-65 minutes at 350°F, or until bread is golden brown and toothpick inserted in the middle comes out clean.
Transfer bread to a cooling rack and cool in the pan 5 minutes. After 5 minutes, turn bread out of the pan, turn right side up. Serve warm or at room temperature.