01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper or lightly oil a baking dish.
02 - Arrange the salmon fillets, skin-side down, on the prepared sheet. Season each fillet with salt, pepper, and a drizzle of olive oil.
03 - Spread 1 tablespoon of pesto evenly over the top of each salmon fillet.
04 - Scatter the halved cherry tomatoes and red onion slices (if using) around the salmon. Drizzle the remaining olive oil over the vegetables. Season with salt, pepper, and lemon zest.
05 - Bake for 15-18 minutes, or until the salmon flakes easily with a fork and the tomatoes are soft and blistered.
06 - Serve hot, garnished with fresh basil leaves and lemon wedges.