If you stored a tomato based product, such as pasta, in a plastic container, chances are your Tupperware is stained. If you heated the pasta in the microwave using the same container, chances are your plasticware is stained permanantly. Washing the dishes will help, but your containers may be stained beyond repair. To avoid this, spray your bowls or containers with a no stick cooking spray before each use to keep your plastic containers from getting stained from red sauces.In addition, one should never place a tomato based product in the microwave if one is using a plastic container. Because the plastic is so pourous, the tomato gets embedded in the pores. If a container is already stained, you have to get a little creative when washing the dishes. Your first option is to fill the bowl with hot water and drop in a couple of denture tablets. Leave for a couple of hours and when you come back the stains will hopefully be removed. You can also try soaking the container in one part bleach to two parts of water. Make sure you give the bowls a thorough rinse, maybe even a run through in the microwave, before using again.