In a large dish or zip-top bag, combine lemon juice, zest, olive oil, garlic, oregano, cumin, pepper, and salt. Add lamb steaks and coat with marinade. Refrigerate 2 – 4 hours.
When ready to cook, allow lamb to come to room temperature and drain marinade.
Preheat bbq grill or a heavy-based pan to high. Cook lamb steaks 3 – 5 mins per side, or until cooked to your liking. Transfer to a plate and rest 5 mins.
Combine salad ingredients (cucumber through olive oil) in a bowl, and toss well. Season to taste with salt and pepper.
Thinly slice lamb steaks, and mix with any resting juices.
Warm tortillas according to packet directions. Serve lamb with tortillas, tzatziki, tomato salad, feta, jalapeños, and lime wedges.