In a large bowl, add the minced garlic, olive oil, lemon juice, cumin, paprika, turmeric, Aleppo pepper, salt, and pepper. Mix well. Add the chicken to the bowl and combine everything making sure the chicken is well coated. Place in the fridge for at least 2 hours; you can leave it overnight for the best flavor.
Preheat the oven to 425 degrees.
Place the marinated chicken on a baking sheet with the chopped red onion. Bake in the oven for 20 to 25 minutes until the chicken is cooked through and very slightly crisped on the edges. Remove from the oven and set aside to cool for 10 minutes. Once the chicken has cooled, carefully cut it into slices and place it on to a serving dish with all the red onion and juices from the baking sheet. Top with chopped parsley and enjoy.