01 - Preheat the oven to 400°F. Line a baking sheet with parchment paper or lightly grease a baking dish.
02 - Arrange the salmon fillets on the prepared sheet, leaving space between each piece.
03 - Spread 1–1.5 tbsp of pesto over each fillet, coating the top evenly.
04 - Scatter the halved cherry tomatoes and sliced red onion (if using) around the salmon.
05 - Drizzle olive oil over the tomatoes and onions. Season everything with salt and pepper.
06 - Bake for 15–20 minutes, or until the salmon flakes easily with a fork and the tomatoes are softened. (Thicker fillets may need a few extra minutes.)
07 - Serve hot, garnished with lemon wedges.