Preheat the oven to 350º Fahrenheit (175º Celsius). In a roasting pan, line with parchment paper or foil and spread red onion slices, lemon slices, rosemary, and garlic cloves over it.
Rub the turkey leg with olive oil (both sides).
In a small glass bowl, add paprika, garlic powder, dried oregano, ground cumin, salt and pepper and mix well to combine all the ingredients together.
Sprinkle the spices mixture over the turkey on both sides.
Place the turkey leg on top of the slices of onions, lemons, rosemary and garlic, skin side down and roast for 30 minutes. Turn the legs over, skin side up, and cook for a further 30-40 minutes or until the internal temperature is 165°F.
Remove the turkey from oven, wrap with foil and let it rest for about 20 minutes. Enjoy!