Begin by removing any excess moisture from the salmon fillet with a paper towel and sprinkle the salmon fillet with salt and pepper. Set aside.
Next, prepare the marinade by placing olive oil, lemon juice, dijon mustard, honey, dill, salt, and garlic into a bowl and whisking until all the ingredients are combined.
Place a large piece of tin foil onto a baking sheet or into a 9x13-inch pan and make sure the edges of the tin foil are folded up so no liquid can escape. Pour the marinade onto the bottom of the tin foil.
Place the salmon fillet skin side up into the marinade and let it sit for 15-30 minutes. You don't want to marinate your salmon too long, so make sure not to leave it overnight.
While the salmon is marinating, preheat the oven to 375ºF.
Next, flip the salmon fillet over to skin side down and lay lemon slices and fresh dill sprigs on top of the salmon.
Carefully, wrap the salmon in the tin foil by folding all the edges in so no air can escape (you may need to add another piece of tin foil to keep the air in).
Place salmon in the oven and bake for 25-35 minutes. The cook time varies by how thick the salmon fillet is. This salmon fillet was about 2-inches thick and needed 35 minutes to bake.
While the salmon is baking prepare the tartar sauce by adding all the ingredients into a bowl. Mix the ingredients together and place the tartar sauce in the refrigerator.
When the salmon bake time is up, check to see if the salmon is fully cooked. The salmon will be done when it turns a pale pink and is easily flaked with a fork.
Remove the salmon from the oven and remove the dill and lemon slices from the tin foil. Turn oven to broil.
Carefully lay 2 tablespoons of cold butter over the top of the salmon and place the salmon in the oven (uncovered) for an additional 2-5 minutes (depending on the strength of the broil). The goal of the broil is to melt the butter and end up with a caramelized top on the salmon.
Remove from the oven and let rest for 5 minutes. Then, serve the salmon with tartar sauce.