Slice all the vegetables into strips and chop the tomato. Put some oil in a pan and add the onion. Let it cook for a few minutes on a medium heat, add the rest of the vegetables, a splash of wine and cook for 5 to 10 minutes more.
Add pieces of cod, more wine and a sprinkle of dill. Add salt if you wish, personally I think it doesn't need it.
Let it simmer for 15 to 20 minutes on a medium heat turning the cod once. Add a little water when needed. The vegetables shouldn't be too soggy and there should be some sauce.
I do it in a large non-stick frying pan it's better than a saucepan.