Heat the oven: Set to 400°F (200°C). Line a rimmed baking sheet with parchment or foil for easy cleanup.

Prep the salmon: Pat the salmon dry with paper towels. Place it skin-side down on the prepared sheet. Rub the top with olive oil and season with salt and pepper.

Make the herb butter: In a bowl, combine softened butter, minced garlic, lemon zest, lemon juice, parsley, dill, chives, a pinch of red pepper flakes (if using), and a pinch of salt and pepper. Mix until creamy and well combined.

Spread the butter: Dot and gently spread the herb butter all over the salmon in an even layer. Tuck lemon slices along the sides and a few on top, leaving some areas uncovered so the fish can brown.

Roast: Bake for 10–14 minutes, depending on thickness. A center-cut fillet about 1 to 1.25 inches thick usually finishes in 12 minutes. The salmon is done when it flakes easily and reaches 125–130°F for medium (use an instant-read thermometer).

Optional broil: For a lightly caramelized top, switch to broil on high for 1–2 minutes. Watch closely so the butter doesn’t scorch.

Rest and finish: Let the salmon rest 3–5 minutes. Spoon any melted herb butter from the pan over the top. Squeeze extra lemon if you like, and sprinkle with fresh herbs and flaky sea salt.

Serve: Slice into portions with a thin spatula. Serve with roasted potatoes, steamed green beans, buttered rice, or a citrusy salad.