Roast vegetable pasta. The other night I chopped up a handful of mushrooms, a few tomatoes, a bunch of asparagus, some olives and half an eggplant. Into a baking tray with oil, salt, pepper. Cooked some pasta. It was was under two minutes prep and delicious.
Lentil soup or as I call it 'poverty soup'. I lived off this when I was poor and still love it. An onion, garlic, carrot, pumpkin, zucchini, potato/sweet potato, cup of red lentils, curry powder, veg stock if you have it or just water, s+p, bay leaf, coriander. A few minutes prep, couple of minutes cooking off onion/garlic, then throw everything else in with 4 cups of water. So easy and cheap.
Or of course, mashed potato and baked beans.