Preheat the grill and spray a grill pan liberally with butter spray (or nonstick spray).
In a small bowl or mortar and pestle, combine the garlic, lemon juice, rosemary, salt and pepper. Use the pestle or the end of a small glass to crush the garlic and rosemary into the lemon juice, creating a paste.
2 cloves minced garlic, 1 tablespoon lemon juice, 1 tablespoon finely minced fresh rosemary, 1 teaspoon coarse sea salt, ½ teaspoon ground black pepper
Spread the garlic paste over each piece of salmon, using it all. Allow to chill in the fridge for 20 minutes with the paste over the salmon.
4 (6-ounce) salmon filets
Remove salmon from the fridge and spray each piece of salmon 4 times with butter spray.
Butter spray
Flip the salmon over so it's skin side up on the grill pan and spray the bottom of each piece with more butter spray.
Grill, covered, for 4-5 minutes, then flip each salmon filet. Spray again with butter spray (about 2 sprays per filet) and cover again, cooking for an additional 6-8 minutes.
Once salmon is fully cooked through (it will be flakey and have an internal temp of at least 145°F), remove it from the grill and serve.