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