Step 1

Arrange an oven rack about 6 inches below the broiler, then set the oven to broil. Line a rimmed baking sheet with aluminum foil.

Step 2

Drizzle the oil over the skin of the salmon fillets and rub to evenly coat. Place skin-side down on the prepared baking sheet.

Step 3

Combine the Dijon mustard, whole-grain mustard, rosemary, thyme, salt, and pepper in a small bowl. Divide the mixture evenly among the salmon fillets and spread to coat.

Step 4

Broil until the salmon is cooked through and flakes easily, 6 to 8 minutes. An instant-read thermometer into the middle of the thickest fillet should read 120°F to 130°F for medium-rare, or 135°F to 145°F for well-done. Total cook time will depend on the thickness of salmon. Squeeze the lemon half over the salmon and serve.