Waffled Banana Bread

Name: Waffled Banana Bread
Ingredients: 1 1/4 cups all-purpose flour; 3/4 cup sugar; 1/2 cup chopped walnuts; 1 teaspoon baking powder; 1/2 teaspoon baking soda; 1/2 teaspoon ground cinnamon; 1/2 teaspoon freshly grated nutmeg; 1/4 teaspoon fine salt; 1 cup smashed banana (2 to 3 small bananas); 1/2 cup vegetable oil, plus more for brushing waffle iron; 1/2 cup sour cream or Greek yogurt; 1 teaspoon pure vanilla extract; 2 large eggs; Soft unsalted butter and confectioners' sugar, for dusting, optional