It's an organic compound present in tomatoes called carotine that is liposoluble but hydrophobic so the normal water and dish soap rolls right over it. In order to get rid of it pour a good amount of oil and dish soap into the Tupperware and scrub all over with a paper towel, rinse and behold the magic
I would argue it's also because most plastic isn't actually very smooth and these oils get caught in the "pores." It's much harder to remove spaghetti stains from tupperware than from glass.
No nonsense from my glass containers. Glass is non-reactive so you can really put anything in it without issues. Acid (like tomatoes) tend to take on a metallic flavour from metal containers like stainless, and plastic can melt if your not careful.
This reads like a word puzzle, with the random mention of dawn at the end. What's the time of day got to do with it xD We're washing containers not casting a spell :-P
The tomato sauce has lycopene (sp? ) in it, which is a hydrophobic molecule, making it very difficult to just wash off. You can take a stick of butter on rub it all over the inside of the container, then put a paper towel in and fill it about half the way with water. Then put the lid back on and shake the shit out it. You should get it pretty cleaned off that way.
So far literally no one has said the real and correct way to remove the stains. Fill sink with some water. Add bleach, let me soak for an hour or so. Perfectly back to normal. For particularly bad stains, soak overnight. Any decent restaurant or kitchen bleaches their kitchen utensils and containers. Back when I had my food handlers card many moons ago bleaching was required.
Cost the interior with butter. Put some dish soap after and fill with a little water. Place a paper towel in. Close and shake vigorously for a few minutes. Should be clean after