Cut salmon in portions for each guest. I cut in half, as it was 2 of us. Preheat oven to 400.
Mix garlic salt, paprika, olive oil in melted butter. (Note: I used a very good garlic salt from Penzey's. If you don't have a high quality, I would advice using sea salt on the salmon first & then adding some garlic to the sauce separately.)
Spray a piece of aluminum foil w/ cooking spray. (Use one large piece of foil for each piece of salmon.) Put a piece of salmon in the foil.
Brush each piece of salmon w/ the butter sauce. If you have any left-over, drizzle over top. Add some lemons & onion slices to each piece of salmon. Fold loosely the foil over to make a foil packet.
Bake for about 15 mins. or until the salmon is done & flaking to your liking. Enjoy!