Spaghetti with a basic tomato sauce (tinned tomato, red onion, a little garlic, a finely chopped salted chilli) little bit of feta cheese on top, ready in 15 minutes.
Or a toasted cheese and red onion sandwich (bread is first toasted while the red onion is fried in a little butter) grated cheese, and red onion in the sandwich then into the frying pan with some more butter, I tend to place a weight on top of the toasted sandwich in the pan and cook for a minute each side, just enough time to start to melt the cheese. Served with a pint of whatever I have in a keg.