dried wholemeal pasta
tinned tuna (tuna + butter beans + chopped onion = substantial salad)
tinned sardines in olive oil (can be mashed and dumped on pasta, SHUT UP YOU SARDINE-HATING PEOPLE IT'S NICE)
tinned beans (e.g. butter beans, chickpeas)
a jar of pesto or other pasta sauce
eggs (then I can make omelettes, scrambled eggs, etc.)
onions, garlic, assorted spices
frozen edamame (I can eat a large bowl of edamame with sea salt as a meal without anything else at all)
basmati rice