1. Rub the lemon juice and salt all over the chicken.
2. Heat the oil in a heavy-bottomed frying pan over medium heat; add the onion and cook until the they start to brown. Add the ginger, garlic and green chilies and cook for 2 minutes, or until soft. Add the almonds, paprika, turmeric and garam masala. Cook, stirring frequently for an additional minute. Allow the onion mixture to cool completely.
3. Place the cooled mixture in a food processor along with the cilantro, grind to a smooth paste. Rub the paste thoroughly all over the chicken and inside the cavity. Cover and refrigerate for 6 to 8 hours.
4. Preheat the oven to 400° F.
5. Soften the banana leaves by dipping them into hot water. Wipe the pieces dry as they become pliant. Tie the legs of the chicken together to keep them in place.
6. Wrap the chicken in the banana leaves, making sure that it is well covered. Tie a piece of kitchen string around the chicken like a package. Place the chicken in a roasting pan and bake for 1 hour, until the chicken is cooked and tender.
7. Unwrap the banana leaves from around the top of the chicken, baste the chicken with some of the juices and return it to the oven for 10 minutes until brown.