I would just scrub it really well again...Sometimes Coca-Cola works good to remove rust. When you are done using it for Apple sauce, wash it by hand, let it sit overnight to make sure it is 100% dry, and rub it down with a food grade oil..mineral oil is good. Store it covered up in a box or a fabric bag...like an old pillow case. Don’t use plastic bags.
The next time you use it, you will only need to wash off the oil. There will be no rust.