Preheat your grill to between 400 and 500° (every “expert” will tell you something different).
Meanwhile, combine the sour cream, dill, minced onion, and salt. (Hint: I use 8 shakes of each spice and taste until I get to the flavor I'm looking for. You will need much less salt than dill and minced onion.)
When you start the cooking process, be ready to roll because this will only take 6-8 minutes.
Lay a sheet of tin foil over the grill and coat liberally with cooking spray.
Lay the salmon on the grill skin side down. Season the top with a dollop of butter or margarine and a few conservative squirts of lemon juice.
Close up the grill and cook for 3-3 ½ minutes depending on the heat of your grill.
When this time has passed, salt and pepper the salmon and flip it over, cooking for another 3-3 ½ minutes.
When this time has passed, flip the fish back over and use a meat thermometer to check its internal temperature (it should be at 135°). If it's not quite there, close the grill back up and cook for 1 minute increments until the fish has reached it's optimal temperature.
After transferring to plates, top the fish with the dill sauce or serve it on the side. (I would recommend plating the salmon with the skin still on. This will keep the salmon from falling apart in the transfer.) Feel free to garnish with scallions/green onion if you have them too.