Get the juice out of the oranges and lemon. Put them together in a bowl and add the achiote paste. Then using a nutri bullet or hand blender, blend the achiote paste with the orange and lemon juice until all the achiote has dissolved.
Place the pork meat in a large bowl and add the achiote marinade. Marinate over night or at least 2 hrs before cooking.
To use the banana leaf, turn on a hob burner and pass the banana leaf over the fire, making sure not to burn it. It will go shiny and flexible. Place it in a dutch over (cast iron casserole) and add the pork with the achiote marinade, the ¼ cup of water, the onion, salt, garlic, dried oregno and wrap it very well. Put the lid on and place in the oven to 160° C.
Cook for 1 hr and take it out to check if it needs more seasoning. Place the casserole back in the oven and cook for one more hour or until the pork is very tender that it falls apart.