Preheat grill or barbecue to medium-hot. Season tuna steaks with half the salt and pepper. Combine jam and mustard in a small cup; spread one side of the tuna steaks with half of the jam mixture.
Place the corn, tomato and zucchini in the centre of each of four 30 cm squares of aluminium foil, dividing them equally. Sprinkle the vegetables evenly with the garlic, remaining salt and pepper, the chillies and the oil. Fold edges of foil over to form tightly sealed packets.
Grill or barbecue the tuna and the vegetable packets 10 cm from heat for 4 minutes. Turn tuna over. Spread with remaining jam mixture. Cook until tuna is opaque in the centre and flakes when touched with the tip of a fork, 4 to 6 minutes. Open the vegetable packets carefully to avoid the steam that will escape. Serve with the tuna steaks.
on the menu
A crisp salad containing peppery watercress, sliced red cabbage and mixed green leaves makes a good accompaniment to this robust fish dish.