Preheat oven to 400°F (204°C). Line a rimmed baking sheet with parchment paper, aluminum foil, or a silicone baking mat. If using aluminum foil, brush lightly with olive oil.

Arrange salmon fillets evenly spaced in the middle of the pan. If also roasting vegetables, arrange them around the perimeter of the pan, as pictured above.

In a small saucepan or skillet over medium heat, melt the butter with the olive oil. Add the garlic and cook for 1 minute, until fragrant. Remove from heat and stir in the lemon juice, herbs, salt, and pepper. Spoon mixture evenly over the salmon fillets (and vegetables, if using). If desired, place a lemon slice on top of each salmon fillet.

Bake for 15–20 minutes, depending on salmon thickness (about 10 minutes per 1-inch thickness measured from the thickest part of the fillet). Salmon should be opaque and flake easily with a fork; if you want to check it with an instant-read thermometer, internal temperature should reach 145°F (63°C).

Serve warm. Store leftovers tightly covered in the refrigerator for up to 3 days.