Line a large baking sheet with a piece of heavy-duty aluminum foil (or double the foil) 6 inches longer than the salmon and lightly spray the foil with cooking spray.
Place the salmon, skinless side down, in the center of the foil and fold the foil up snugly around the fish; set aside.
In a medium bowl, whisk together the orange juice, honey, Dijon mustard, yellow mustard, brown sugar, olive oil, soy sauce, minced garlic, 3/4 teaspoon salt, smoked paprika, the dried herbs and spices (1/2 teaspoon each of parsley, oregano, thyme, onion powder, and pepper), and cayenne.
Pour the marinade evenly over the salmon, cover the packet, and let the salmon marinate at room temperature for 20–40 minutes.
During the last 15 minutes of marinating, preheat the grill to 375–400°F with the lid closed.
Evenly scatter the cubed butter over the top of the salmon, place a second piece of foil over the fish, and fold the edges under to form a sealed packet with a small tent for air circulation.
Carefully transfer the foil packet to the preheated grill and close the lid. Grill for 15–20 minutes depending on thickness, or until an instant-read thermometer inserted into the thickest part reads 130–135°F (about 10 minutes for 1-inch thick; about 20 minutes for 1½-inch thick).
Using a spatula, slide the hot foil packet back onto the baking sheet. Carefully open the top foil away from you to avoid steam, spoon the buttery sauce from the packet over the salmon, and let the salmon rest for 5 minutes before slicing.
Season to taste with additional salt and freshly cracked pepper and serve.