How do I clean tomato sauce stains from tupperware (and other types of plastic storage)?

We have a recurring problem where we have permanently stained tupperware from sauces (usually tomato). This stems from the fact that when we make homemade pasta sauce or chili, we make a large batch and freeze some for future dinners (to make life easy). Then, of course, we end up microwaving the container, and in the end, it is so stained that lots of vigorous cleaning won’t get out the stains. Short of throwing out the items, is there any way to remove the stains and/or prevent them from developing?