Some great soups have resulted from the "grab whatever veg are in the fridge and shove them in a pan" method.
Pasta and lentils is one of our favourites. It's an Egyptian recipe, originally called rishta bi ads. Slice/chop an onion, sauté it in olive oil with ground cumin, coriander and cinnamon, add a tin of green or brown lentils, season with salt and pepper, and serve on pasta with a dab of butter/marg. This makes 2-3 servings depending on how hungry you are, it's very easy, and it's great comfort food.