Prepare the masa: In a large mixing bowl, combine masa harina with chicken broth gradually, mixing until you achieve a smooth, thick consistency. Add vegetable oil, salt, and ground cumin. Mix thoroughly and set aside.

Marinate the pork: Cut pork into 2-inch chunks. In a bowl, combine lime juice, minced garlic, cumin, oregano, salt, and black pepper. Add pork pieces and marinate for at least 30 minutes.

Prepare vegetables: Dice potatoes into 1-inch cubes. Slice bell peppers and onions. Quarter tomatoes. Measure out rice and set aside.

Prepare banana leaves: Pass banana leaves briefly over an open flame or hot burner to make them pliable. Cut into 12-inch squares. Clean and dry thoroughly.

Assemble nacatamales: Lay a banana leaf square flat. Spread about 1/2 cup masa in the center, forming a rectangle. Place a piece of marinated pork in the center. Add 2 tablespoons rice, potato cubes, bell pepper slices, onion, tomato, and a sprig of cilantro.

Wrap securely: Fold the banana leaf over the filling, then fold in the sides to create a tight packet. Tie with kitchen string.

Steam the nacatamales: Arrange wrapped nacatamales in a large steamer pot, standing them upright. Add water to the pot (not touching the nacatamales). Cover tightly and steam over medium heat for 3 hours, checking water level periodically.

Test for doneness: After 3 hours, carefully unwrap one nacatamal. The masa should be firm and pull away from the leaf easily. The pork should be tender.

Serve hot: Remove from steamer and let rest 5 minutes before serving. Serve in the banana leaf for authentic presentation.