Basic/quick/adaptable Spag bol.
Put pan of water onto boil for pasta (doesn't have to be spaghetti, could be any shape). When it boils, add pasta and cook it...
While you wait for the water to boil....
Chop onion, fry in olive oil. Add minced beef and stir about until all browned.
Add tinned tomatoes (Half a big tin is enough for one) to beef and onion and a good squirt of tomato purree and black pepper and a dash of mixed herbs.
Simmer the sauce for as long as it takes your pasta to be cooked. Drain pasta, put on plate or a in bowl, tip sauce over the top.
The adaptable bit is all the other things you can bung in. I usually add one or all of the following - red or yellow pepper (diced up and fried in with onion), black olives from a jar, tinned (or frozen) sweet corn. You can also replace the beef with diced up strips of bacon or chicken (ok, it's getting well away form a spag bol now, but...) or leave out the meat stage and once the tomatoes are in, add cooked chicken, or tinned tuna. Or leave out the meat altogether and bung more veg in. Add chilli powder and red kidney beans (or even baked beans) for a chilli con carne version.
I usually bung this together in 20 minutes. I know it should really all be simmered for ages to let the flavours develop, but I can't be bothered, and it works fine for me, and no one I've served it to has ever complained.
Or there's poor man's (well, poor Arch's) kegeree. Cook long grain rice, hard boil a couple of eggs. Chop eggs up, and flake up a tin of mackeral (in oil or brine) with a fork. When rice is cooked, mix in the mackeral and egg, along with a nice dollop of butter and if you fancy spice, a little curry paste (the sort in jars).
And then there's curry - easy if you use a paste. Fry onion, add in whatever meat and brown that, add any veg, add curry paste, then liquid (stock, or tinned tomatoes) and simmer. Thicken with cornflour if you need to, or yoghurt....