Heat the oven and line the pan: Preheat the oven to 400°F and line a rimmed sheet pan with parchment paper or foil, which saves you the scrubbing later.

Dry and season the fillets: Pat the salmon completely dry with paper towels on both sides. Rub each fillet with the olive oil, then season all over with the salt, pepper, and garlic powder. Arrange them skin side down on the pan with about an inch between fillets so they roast instead of steam.

Mix the lemon garlic butter: In a small bowl, stir together the melted butter, minced garlic, lemon zest, lemon juice, and chopped dill.

Spoon it over the fish: Spoon the butter mixture evenly over the fillets, letting it pool on top and run down the sides. Tuck the lemon rounds around and between the fillets.

Bake and check early: Bake for 12 to 15 minutes depending on thickness. The salmon is done at 145°F on an instant-read thermometer inserted into the thickest part, or when the center has turned opaque and the flesh flakes apart when you press it with a fork. Start checking at 12 minutes.

Rest and serve: Let the fillets rest on the pan for 3 minutes, then spoon the buttery pan juices back over the top and sprinkle with parsley. Serve with the roasted lemon rounds for squeezing.