Boil the potatoes for 10 mins until tender, then drain. Heat oven to 200C/180C fan/gas 6. Toss the potatoes in the oil, then transfer to a baking tray. Roast for 20 mins. Push the potatoes to one side and put the courgette, pepper, spring onion and pine nuts down the middle of the tray. Put the salmon on the other side. Squeeze lemon juice over the fillets and the vegetables (not including the potatoes). Season everything with pepper. Spread each of the salmon fillets with pesto and return the tray to the oven for 12-15 mins until everything is cooked through.