01 - Heat the oven to 400°F. Prepare a baking tray with parchment paper or lightly oil it.
02 - Place salmon fillets on the tray and season both sides evenly with salt and pepper.
03 - Spread 1 tablespoon of basil pesto over the top of each fillet.
04 - Distribute the halved cherry tomatoes and red onion slices (if using) around the salmon fillets.
05 - Drizzle olive oil over the tomatoes and onion, then arrange lemon slices atop the salmon and vegetables.
06 - Bake for 15 to 18 minutes until the salmon flakes easily with a fork and is cooked through.
07 - Remove from oven, garnish with fresh basil leaves if desired, and serve immediately.