I prefer it this way...
Thin slice an onion and a lemon. Put a layer of those on a piece of foil. Lay the filet on top of them and season with Tony C's. Put another layer of the onion and lemons on top of the seasoned fish along with a couple of pats of butter. Leave the foil open but turn the edges up (to keep the juices). Grill until a fork flakes the meat. The butter and juices from the onion/lemons on top will keep the fish moist and cook down onto the onions under the fish. That bottom layer is delicious and will keep the fish from being over cooked. The foil eliminates the problem of the meat sticking to the grill/grate.
I do mine almost exactly like this except I also use some dill with my onions and lemons. Sometimes if it is just me and the wife I will also add some Jalapenos on the top and also I will do this in my smoker using some Pecan wood for about 2 hours or until it flakes.