Preheat your oven to 375°F (190°C). This ensures that the salmon cooks evenly and thoroughly.
Cut a large piece of aluminum foil, about 18 inches long. This will be used to create a packet for the salmon.
In a mixing bowl, combine the melted butter, brown sugar, lemon juice, Dijon mustard, garlic powder, onion powder, salt, and dried thyme. Whisk until smooth and well combined.
Lay the salmon filets on the center of the foil. If you have skin-on filets, place them skin-side down.
Brush a generous amount of the glaze over the salmon, making sure to cover it well. Reserve a little glaze for later.
Place lemon slices on top of the salmon for added flavor and moisture during baking.
Fold the sides of the foil over the salmon to create a sealed packet. Make sure it’s tightly closed to trap all the steam inside.
Transfer the foil packet to a baking sheet and bake in the preheated oven for 20 to 25 minutes, depending on the thickness of your salmon. The fish should be opaque and flake easily with a fork.
Carefully open the foil packet (watch out for hot steam!) and drizzle any reserved glaze over the salmon. Garnish with freshly chopped parsley before serving. Enjoy your Baked Salmon In Foil with your favorite sides!