Mark's Killer BBQ Salmon

Why I Love This Recipe
This is my Uncle Mark's salmon recipe. He is a fisherman up in Washington, and created this amazing recipe.
Ingredients You'll Need
1 Cup Butter
6 Cloves Garlic, minced
4 TBSP Soy Sauce
2 TBSP Grey Poupon Dijon Mustard
1/4 Cup Catsup
Dash of Worchester sauce
Squeeze of Lemon
Montreal" Steak seasoning (or any other)
garlic powder
thinly sliced red onion slices
Directions
In a Sauce Pan combine all of the above, cook on low until bubbly. (One batch of sauce is good for one side of salmon.)
Season Salmon with "Montreal" Steak seasoning (or any other) and garlic powder. Build a tin foil pan, or boat, out of heavy duty foil. Place foil boat on the grill, place fish on foil, cover with sauce and thinly sliced red onion slices.
Cover grill and cook until fish is firm, but not over done. (about 15-20 minutes) Make sure that the sauce does not burn. Enjoy!
Note: This works best with salmon with the skin on.