Preheat the grill or barbecue. Lay the sardines or mackerel in a shallow dish. Make several diagonal cuts across the flesh of each fish and season with salt and pepper. Now brush most of the Saclà Classic Pesto over the skin of the fish and inside the cavity. Sprinkle with pine nuts and drizzle with the juice of a lemon. Place the fish under a preheated grill or onto a hot barbecue and cook for 8-10 minutes, turning once and basting with any remaining pesto.