Combine the lemon juice, olive oil, garlic, salt, and spices in a large bowl, then whisk to combine. Add the chicken, and toss well to coat. Cover, and marinate in the refrigerator for at least 1 hour and up to 12.
Preheat the oven to 425ºF. Line a rimmed sheet pan with parchment paper.
Place the chicken and onions on the pan forming an even layer. Roast until crisp around the edges and cooked throughout, about 45 minutes.
Allow the chicken to cool for 5 minutes before slicing. Serve with parsley.