Chop the meat into cubes, chop the onion into small dices, transfer the meat and the onion to a bowl, add salt, oregano and black pepper, mix it all together very well, until the spices incorporate into te meat.
Into a pan, add all the meat with the spices, stir for 1 minute and let it cook for 7 minutes over medium-low heat.
Cut the oranges into round slices, spread them on the bottom of a baking dish, forming a layer. Transfer the meat to the baking dish and cover it with another layer of oranges.
Bake in a preheated oven at 200°C (392°F) for 25 minutes.
Serve.