Preheat a grill or barbecue to high heat. Once hot, cook beef on both sides for 3-4 minutes on each side, or until cooked to your liking. Set aside on a plate loosely covered with foil to rest for 5 minutes. Thinly slice beef.

Meanwhile, toss sweet potato, zucchini and onion with ½ tbsp of oil to coat. Add vegetables to the grill over high heat for 1-2 minutes each side, or until tender and lightly charred.

Plate sliced beef and vegetables on a plate and drizzle with remaining ½ tbsp oil and lemon juice, lemon zest, feta and pine nuts.