I am not sure you can call it simply just because you have few ingredients, some of the more complicated things to cook , that take both time and several steps to do has few ingredients.
But if you talk about quick meals to prepare , that take little time and not a lot of appliances to use or can be cooked without using a blender and such, then I have a few.
Oven baked , shredded cabbage, onion ( and carrot if you like), you can saute this in a bit of oil and a half cup of wine or apple juice until soft first if you like, just water can also be used, but you don't have to if you like it crunchier, or just bake it for 15 minute's before adding the rest of the ingredients. Slice the champignon's and sweet potato and then top it all with cheese.
Tomato soup: 2 tins of chopped tomatoes , chopped onion , garlic and a bit of oil and water + herbs. Bread on the side.
Stew: Chopped potatoes, carrots or swede(rutabaga), cabbage ,onion and some sort of beans or lentil , add water and cook for 20-40 minutes add pepper and salt and spice if you like.
Potato"porridge" : Cook ( or already cooked) potatoes in a bit of water, add flour and more water, into a thick porridge, not a mash. Serve with a big slab of real butter in the middle. You might use this with a soup on the side.