Slice steak into thin strips.
Prepare a marinade for the steak. Combine the lemon juice, 1/2 cup olive oil, garlic, salt, pepper, cumin, paprika, turmeric, cinnamon and red pepper flakes in a large bowl, then whisk to combine. Add the steak and toss well to coat. Cover and store in refrigerator for at least 1 hour and up to 12 hours.
When ready to cook, heat oven to 425 degrees. Use the remaining tablespoon of olive oil to grease a rimmed sheet pan. Place marinated steak on tray. Add the quartered onion to the marinade and toss once to combine. Remove the onion from the marinade, and place on the pan with the steak, spreading everything evenly across it.
Put the tray in the oven and roast until steak is browned, crisp at the edges and cooked through, about 30 to 40 minutes. Remove from the oven, allow to rest a few minutes before serving. Scatter the parsley over the top for garnish.