Being a bachelor, I often chop an onion and end up with like 4 or 5 meals worth of onion chops, so a lot of "lazy meals" are "get some chopped onion out of the fridge."
How much onion do you use per meal? I feel like I may be using too many, since everything in a grocery store that is sold in bundles or bags, is too much for me and it would likely go bad before I can eat it all, but onions (and plain yoghurt) are the exception. A 10 kg bag of onions lasts a week or less when feeding only myself.