Banana Bread Crumb Cake Ingredients Crumb Filling and topping 1 cup cold butter, cubed 2 cups light brown sugar 2 cups all purpose flour For the Coffee Cake: 2 cups all purpose flour 3 teaspoon baking powder 1 teaspoon cinnamon 1 teaspoon salt 3 ripe bananas, mashed 1/2 cup unsalted butter, room temperature 2