Here’s kittenpie’s kid-friendly lunchtime suggestion:
We precook pasta, veg, and lentils or beans and store them in bins in the fridge. Then, when we need to pack a meal quickly, we grab a handful of each, put it in a small lidded bowl, and mix it with baby food veg puree as a sauce/binder for our quickie casserole-type dish. We also like to give our little girl a small cup of puree to use as dipping sauce for pasta or as pasta sauce. Pure veg and no salt or other additives makes this a great alternative to regular pasta sauce.