Put the fillets side by side in a dish, mix together the soy sauce, garlic, ginger and five spice and spoon it over the fish to cover it evenly. Set aside for 30–60 minutes, turning the fillets once, and spooning the marinade over any bits that are still white.
Meanwhile, make the salsa. Discard the flesh of the lemon and cut the peel into dice. Combine with the olives, pumpkin s