Cut the tops off the peppers, and remove the seeds and ribs. Rub them in a little oil, and place them cut-side down in a baking dish. Roast for about 30 minutes at 170°C (Gas Mark 3 / 325°F), until they are fairly soft but still holding their shape.
Turn the peppers over, and add some refried beans to each pepper, until they are around half full (around 2tbsp per pepper, depending on their exact size). Press the beans right into the base of the pepper. Fill each pepper nearly to the top with cooked rice, and squeeze over the lime juice.
Finish each pepper with a little grated cheese and a slice of tomato, then place under the grill (broiler) or back into the oven for a few minutes, until the cheese has melted and begun to crisp up.
Serve topped with some sour cream and plenty of fresh coriander.