A simple baked fish dish -- but if you wanted, you could serve it equally as well as a marinated raw dish. Remove the skin from the fish, slice it small enough, and there’s no need to actually cook the fish at all.
Preheat the oven to 425ºF (220ºC, Gas 7). Cut the snapper fillet into eight pieces. Arrange the snapper portions in a baking dish, so no pieces are touching each other.
The grapefruit here is very important. First slice the top and bottom off using a sharp knife, then carefully remove the skin and the white pith, starting from the top and working down to the bottom, as if you are following the lines of a soccer ball. Once this is all done, and working over a bowl to catch all the juices, slice between each vein to get a perfect segment. Each segment we are going to cut into five portions and place in a dish for later; also reserve all the juice.
Pass the grapefruit juice through a sieve into a bowl. Whisk in the fish sauce, soy sauce, sugar, and grapeseed oil. Spoon half the dressing over the fish, then pop the fish in the oven for 15-18 minutes, or until cooked.
Chop the spring onions finely, placing the green parts into the remaining dressing mixture and the white bits in a separate bowl.
To the dressing, add the Vietnamese mint, parsley, chili and the grapefruit segments; set aside.
To the bowl with the white spring onion bits, add the cucumber, cilantro and mint, then dress with a little dressing.
Arrange the salad around a large shallow serving bowl or platter. Place the snapper portions on top, drizzle with as much dressing as you desire, then serve straight away.