Make a dry rub with the cumin, oregano, salt and pepper.
Rub thoroughly all over the pork tenderloin.
Heat ¼ cup of the sunflower oil in a heavy bottom skillet and brown the pork cubes on all sides. Add in the wine to deglaze the pan, lower the heat to a simmer for about 5 minutes. Remove from skillet and set aside.
Heat the other ¼ cup of oil and sauté the onions, mushrooms, pepper, and carrots for about 5 minutes. Pour ½ cup water into the pan and cook approx. 10 minutes over medium heat, until the vegetables are soft and most of the liquid has been absorbed. Add in the chopped tomatoes and simmer 5 minutes.
Combine all the ingredients together and transfer into the earthenware pot, add the leeks.
Cover the dish with its lid and place in a preheated 250 degree oven for three hours or so.
You could easily do this in a crock pot instead of the oven.
Serve hot.
This recipe is great for left-overs, you may want to double it.