Into a food processor, place all of the ingredients for the Cuban mojo. Pulse until you have a smooth marinade.
IN a 9x13 casserole dish, layer the bottom of the dish with the sliced onions. Place the chicken quarters over the onions so theyre all laying flat. Be sure to place them with the skin facing up.
Pour the prepared Cuban mojo marinade over the top of the chicken quarters. Massage the marinade all over the chicken to make sure its well covered.
Cover the casserole dish with aluminum foil and place in the refrigerator to marinade for 2 hours.
Preheat the oven to 400 degrees F (218 degrees C).
Remove the baking dish from the refrigerator and place the dish in the oven on the center rack. Be sure to leave the aluminum covering on the baking pan.
Bake the chicken leg quarters in the oven for 20 minutes. Remove the aluminum foil and then bake for another 20-25 minutes uncovered. Bake until the chicken's internal temperature reaches 165 degrees F.
Optional step: If the skin is not crispy enough for your liking, place under the broiler for 2-3 minutes to crisp up the skin even more.
Rest for 5 minutes before serving.