Remove the salmon from the refrigerator and let stand at room temperature for 10 minutes while you prepare the other ingredients. Preheat an outdoor grill to medium (about 375 degrees F). Line a rimmed baking sheet (large enough to hold your piece of salmon) with a large piece of aluminum foil. If you prefer your food not to touch the foil directly, lay a piece of parchment paper on top (be sure none of it pokes out when the packet is sealed).
Lightly coat the foil with baking spray. Then, arrange a few sprigs of dill down the middle. Cut the lemons into thin slices and arrange half of the slices down the middle with the dill. Place the salmon on top.
Drizzle the salmon with the melted butter. Sprinkle with the salt and pepper. Scatter the garlic over the top, then lay a few more springs of dill and the remaining lemon slices on top of the salmon. Chop a tablespoon or so of the remaining dill and reserve for serving.
Fold the sides of the aluminum foil up and over the top of the salmon until it is completely enclosed. If your piece of foil is not large enough, place a second piece on top and fold the edges under so that it forms a sealed packet. Leave a little room inside the foil for air to circulate.
Carefully slide the wrapped salmon onto the grill. Close the grill and grill the salmon for 14-18 minutes, until the salmon is almost completely cooked through at the thickest part. The cooking time will vary based on the thickness of your salmon side. If your piece is thinner (around 1-inch thick) check several minutes early to ensure your salmon does not overcook. If your piece is very thick (1 1/2 inches or more), it may need longer.
Open the grill, and carefully open the foil so that the top of the fish is completely uncovered (be careful of hot steam). Close the grill, and continue grilling until the fish is cooked through completely, about 3 minutes more. Watch the salmon closely to make sure it doesn’t overcook. Remove the salmon from the grill (I like to use the foil to lift it right back on top of the baking sheet). If it still appears a bit underdone, you can wrap the foil back over the top, and let it rest for a few minutes. Do not let it sit too long—salmon can progress from "not done" to "over done" very quickly. As soon as it flakes easily with a fork, it's ready.
To serve, cut the salmon into portions. Remove the topmost sprigs of dill and discard. Sprinkle with freshly chopped dill and top with an extra squeeze of lemon as desired.
This recipe is best enjoyed the day that it is made, as salmon usually dries out when reheated. If you have leftover salmon, try serving it room temperature over a salad the next day or flaking and scrambling it with eggs.
TO MAKE DAIRY FREE: Swap olive oil or the oil of your choice for the unsalted butter.
TO MAKE WHOLE30/PALEO: Swap olive oil or the oil of your choice for the unsalted butter
For more tips about how to tell when salmon is done or ideas to vary up this recipe to different tastes, see blog post above.