Heat oven to 325°.

Cut a piece of parchment paper to fit a large baking sheet that will hold the salmon. The parchment paper will make it easier to lift the salmon in one piece from the baking sheet to a serving plate.

Drizzle 2 tablespoons grapeseed oil onto the parchment paper. Scatter sliced onions and half the citrus slices over oil and toss with oil to coat the onions lightly.

Place the salmon skin side down over the onions on the parchment paper. Using a very sharp knife, make deep scores across the salmon into serving portions, making sure to leave about ¼-inch at the bottom including the skin, intact. This will make it easier to serve at the table.

Arrange the remaining half of the citrus slices around the salmon. Drizzle the salmon and citrus with oil, including into the cuts of the salmon. Season with salt and cracked black pepper. Place herb sprigs on top, pressing into the salmon to coat the sprigs with a little bit of the oil.

Roast the salmon until it is barely cooked through — when you poke the center of the fillet with the tip of a sharp, narrow knife and twist it, it is just opaque. Because thickness of salmon filet will determine cooking time, check the salmon with a knife after 20 minutes, then every few minutes until it’s done. The salmon will take anywhere from 30 to 40 minutes.

Transfer salmon, onions, and citrus to a serving platter. Season with salt and pepper and garnish with fresh herbs.

To store leftovers, remove citrus and discard, place salmon in air-tight container or plastic bag/wrap, and keep in refrigerator up to two days.