If you have time to spare, you can ripen bananas in a warm spot in your kitchen. A paper bag can speed up the process. (While I very spotty or fully brown bananas for banana bread, similar to those you'll see in my roasted banana-ripening guide, you'll want this fruit to still be firm enough to slice. So with that in mind, stick to those first two methods and feel free to proceed with this Bananas Foster recipe when you begin to notice brown spots.)