Sour Cream Banana Bread

INGREDIENTS

• 4 very ripe bananas, divided
• 1 cup white sugar
• 3/4 cup butter, melted and cooled
• 2 large eggs
• 1/3 cup sour cream
• 1 teaspoon vanilla extract
• 2 cups all-purpose flour
• 1 1/2 teaspoons baking powder
• 1/2 teaspoon salt
• 1/2 cup chopped walnuts (optional)
• 2 teaspoons white sugar
• 1/2 teaspoon ground cinnamon