Heat vegetable oil in a large skillet over medium heat.
Add the chopped onion and bell pepper and sauté until soft.
Stir in the garlic and cook for another minute.
Add the pork pieces and cook until browned on all sides.
Add the chopped tomatoes, tomato paste, cumin, paprika, oregano, black pepper, and salt. Stir well to combine.
Pour in the chicken broth and bring to a simmer.
Cover and cook for 30-45 minutes, or until the pork is tender and the sauce has thickened.
Stir in the sliced olives, raisins (if using), and chopped cilantro. Adjust seasoning if needed.
In a large bowl, mix the masa harina, vegetable oil (or lard), baking powder, and salt.
Gradually add the chicken broth, mixing until the masa forms a smooth dough.
Cut the banana leaves into squares about 12 inches in size. Heat them over an open flame or in a dry skillet to make them pliable.
Place a small amount of masa dough in the center of each banana leaf square.
Add a portion of the pork filling on top of the masa.
Fold the banana leaf around the filling, securing it by folding the sides and tying with kitchen twine.
Place the wrapped nacatamales in a large steamer or pot with a steaming rack.
Steam over medium heat for 1.5 to 2 hours, or until the masa is fully cooked and firm.
Allow the nacatamales to cool slightly before unwrapping.
Enjoy your meal!