This is one of the easiest fish dishes I make. I've done it with many different fish and it always turns out great. Last night I used butterfish, an unctuous yet firm white-fleshed fish. (However, our old fish ID problem rears its head here - several species bear the name butterfish around the world.)
Anyway, here's the recipe. It just about cooks itself.
Finely chop some peeled ginger, maybe half an inch; and two cloves of garlic. Place in a wide lidded pan with a little oil and sweat them very gently. Do not burn. Add your fish fillets to the pan. Pour over a quarter cup of water, the juice of half a lemon and a very generous squirt of tamari or soy. Throw in some finely sliced onion - or spring onion - and simmer very gently until just done. Don't overcook.
Serve on a bed of rice or noodles with some braised greens on the side - chinese cabbage or broccoli, or regular broccoli.