Remove the salmon from the refrigerator and let stand at room temperature for 10-15 minutes while you prepare the other ingredients.
For the grill: preheat an outdoor grill to medium (about 375℉), and line a large, rimmed baking sheet with a long piece of heavy-duty aluminum foil or a double layer of regular foil. Lightly coat the foil with baking spray, and then place the salmon on top.
Place the butter and minced garlic in a small, microwaveable bowl, and heat in the microwave to melt. Alternatively, you could melt on the stove. Stir in the dill, lemon juice, and zest, and then spread evenly over the salmon. Sprinkle the salmon with the salt and pepper.
Bring the sides of the foil up and over the salmon, folding and sealing at the top and sides, and leaving a little space at the top for air to circulate. If your piece of foil is not big enough, place a second piece on top and fold the edges to form a sealed packet.
Carefully slide the salmon packet onto the preheated grill. Close the lid and grill the salmon for 10-15 minutes, or until the salmon is almost (but not quite) cooked through at the thickest part. Cooking time will vary based on thickness of salmon, and farmed salmon will take a few minutes longer than wild. If your fillet is thin (around 1-inch thick) check on the early side to ensure your salmon does not overcook. If your fillet is very thick, it may need longer.
At this point, carefully open the foil so that the top of the fish is uncovered (be careful of the hot steam). Close the lid and continue to cook until the fish is cooked through completely, about 2-3 minutes more. It’s better to err on the side of undercooked in the previous step. The sealed packet will retain moisture, but the unsealed packet will help you determine when the fish is perfectly cooked. I look for an internal temperature of 120℉ for wild salmon and 125℉ for farmed salmon. Keep in mind the fish will continue to cook for a few minutes after removing it from the heat.
Remove the salmon from the grill. You can use the foil to lift it back onto the baking sheet.
Serve the salmon with an additional sprinkle of chopped, fresh dill and lemon wedges for squeezing, if desired.
For the oven: prepare the salmon as described above, except preheat the oven to 375℉ and bake according to the same times and internal temperatures provided for wild or farmed salmon. When baking, I place the foil packet on a rimmed baking sheet, just in case one of the edges isn’t well sealed and it leaks. Again, cooking times will vary based on thickness of fish, whether it’s wild or farmed, individual oven, and preferred level of doneness; check early and use a quick-read thermometer (or cut into the fish and take a peek) for perfect results.