Yes, you can put undercooked banana bread back in the oven to continue baking and ensure it cooks through properly. It's not uncommon for banana bread (or any other type of bread) to be undercooked in the center while the top and edges appear done. This can happen due to variations in oven temperatures, pan size, or the moisture content of the batter.
If you find that your banana bread is undercooked, follow these steps to salvage it:
Test for doneness: Before returning the banana bread to the oven, use a toothpick or a thin skewer to check the center of the loaf for doneness. If the toothpick comes out with moist batter clinging to it, the bread is not fully cooked.
Preheat the oven: Preheat your oven to the temperature stated in the original recipe or use the temperature you initially baked the bread at.
Protect the crust: To prevent the crust from over-browning while you continue baking, you can cover the top of the bread loosely with aluminum foil.
Return to the oven: Place the undercooked banana bread back in the preheated oven and continue baking. The additional baking time will vary depending on how undercooked the bread was initially. It could take anywhere from 5 to 20 minutes or more.
Check for doneness again: After the additional baking time, use the toothpick or skewer to check for doneness once more. If it comes out clean or with only a few dry crumbs attached, the banana bread is fully cooked.
Cool and serve: Once the banana bread is fully cooked, remove it from the oven, let it cool in the pan for a few minutes, then transfer it to a wire rack to cool completely before slicing and serving.
Keep in mind that if the banana bread is already quite dark on the outside, covering it with foil during the additional baking time can help prevent it from becoming too dark or burnt. Always use your best judgment and check for doneness regularly to achieve the desired level of moisture and doneness in your banana bread.