Create a rub mixture using the olive oil, salt, pepper, half of the diced onion, half of the diced lemon, and all of the parsley and thyme.
Preheat the BBQ grill (a propane system works best because the heat can be controlled at the same temperature throughout the cooking.)
Rinse the salmon (all sides) and pat it dry.
Cut the salmon into 1-inch think steaks against the grain (see photo).
Tear off a sheet of aluminum foil large enough to wrap an individual salmon completely once folded (don't fold it yet, and then place an individual salmon steak in the center of the foil.
Rub the herb mixture over the salmon's surface (both sides)
Place some of the remaining diced onion and lemon slices on top of the steak, then fold the aluminum so that the steak is tightly sealed inside.
Repeat steps 4-6 with all the additional salmon steaks.
Place all the wrapped salmons onto a BBQ grill, medium heat for about 40 minutes, turning often (every 10 minutes) so that it cooks evenly through. Steaks are done when a sample is opened and the salmon is flaky and falls off using a fork.
Cool in the foil off the BBQ foe 10 minutes so that the rub flavors and juices will re-enter the steak.
Open the foil, and remove onion and lemon, and skin if desired.
Serve while still warm and enjoy!