PREPARATION

1. Unfold the banana leaves and rinse under cold running water until soft and flexible, handling gently and being careful not to rip them. Pat dry with paper towels or a kitchen towel. Working on a cutting board, use a small sharp knife to cut the leaves into eight 12 by 6-inch/30.5 by 15 centimeter rectangles. If not using immediately, keep the leaves between sheets of damp paper towels or store in the refrigerator wrapped in a damp kitchen towel. 
2. To make the adobo: Seed, toast, and reconstitute the anchos in water. Drain, reserving 1/4 cup of the soaking liquid. Add the softened chiles and reserved soaking liquid to a blender, along with the garlic, orange juice, vinegar, cumin, oregano, achiote oil, and salt and process into a smooth puree. Set aside. 
3. To prepare the chicken: Season the chicken inside and outside with salt and black pepper. Place in a pot with the water, onion, and cilantro. Bring to a boil over high heat. Lower the heat to medium and simmer for 20 minutes, until just barely tender. Remove the chicken from the broth. Strain the broth and reserve 1/2 cup; refrigerate the remaining broth and save for another use. 
4. Strip the meat from the bones, removing the skin if you like, and cut the meat into 2-inch/5 centimeter pieces; place in a bowl, pour the adobo over the chicken and set aside to marinate for 1 to 12 hours, refrigerating it if marinating for more than 1 hour. 
5. To make the dough: Put the corn in a blender or food processer and process into a smooth puree. In a heavy pot, warm the achiote oil over medium heat. Add the garlic and sauté until lightly gold, about 20 seconds. Add the onion and sauté for about 5 minutes, until translucent and golden. Add the tomatoes, cumin, ground hot pepper, and salt and sauté for 5 minutes more, stirring occasionally. Add the corn puree, broth, milk, and butter and stir to combine. Stream in the cornmeal while stirring continuously and cook for 5 to 6 minutes, until thick and creamy. 
6. Preheat the oven to 350°F/180°C. Line a round 10 by 21/2-inch/25 by 6 centimeter) cazuela or other baking dish with the banana leaves layered in a crosshatch pattern. Spoon in half of the corn dough and cover with the chicken. Add the rest of the dough over the filling and smooth with a spatula. This second layer needs to be just thick enough to cover the filling. Fold the leaves over the top to close. To prevent the leaves from burning, cover with aluminum foil.
7. Bake the tamal for 1 hour, then remove the aluminum foil and bake for 15 minutes more to brown the top and form a delicious crust. If you bake the tamal in a cazuela, do not bother transferring it to a serving plate. Or, transfer it to a large round serving platter or rustic wooden cutting board using two large spatulas. Unwrap the tamal at the table. Slice the tamal into generous wedges or scoop out as you would a spoonbread. Serve with a spoonful of salsa and spoonsful of the pickled onions.